With properly-fitting screwdrivers, no job is impossible. This Winchester was made in 1926, and probably hadn't been apart since then. The right screwdriver made things simple.
If you are drilling, you'll probably be tapping. You'll need taps and a thread gauge.
Taps come in three types, from right to left; taper, plug and bottoming. The taper is easy to start, and he bottom lets you tap to the bottom of a blind hole. The plug is for the inevitable compromises.
A minimum cleaning kit would be a rod and accessories and a cloth to wipe the shotgun down after you are done.
For the interior of the receiver and the trigger mechanism, a regular gun cleaning brush works fine. Usually with a green or black plastic handle, the original design of most brushes dates back to the introduction of the M-16.
All of this cleaning requires solvent. The customary method of providing a cleaning location and solvent supply is with a parts cleaning stand. The sink of the stand rests on a barrel of solvent, which is pumped up into the sink. The parts are scrubbed while in the stream of solvent. The solvent is usually mineral spirits, an inexpensive and non-flammable solvent that usually is reclaimed and has a small percentage of kerosene in it. Only the new, non-reclaimed solvent can be called odorless, and even it has a slight odor to it. Reclaimed solvent that has been used for a while will have a distinct odor to it. The odor is strong enough that on a regular basis we would have people walk into the gunshop and ask “what is that smell?” It wasn't objectionable, but it was noticeable. Even after I would drive home for over half an hour with the truck windows open (tough to do in a Michigan winter) my girlfriend would comment “You smell like a gunsmith.”
A parts cleaning tank, with compressed air nozzle for blowing the solvent off is fast, convenient and messy. The Bassett hound is an option.
Small nicks and scratches can be touched-up with this Outers kit. Extensive bluing requires more of an investment in time, materials and space.
The solvent-soaked parts would be dried by blowing them with compressed air. Between the splashes from the parts washing stand and the compressed air blowing the gunk off, the corner of any shop that uses this method gets dirty. No, it gets grubby and crusted with gunk. And when the drum of solvent gets filled with powder residue, oil, bits of rust and gunk, it has to be properly disposed of. Even as an enthusiastic home gunsmith of your own guns it will take years to use up a drum of solvent, but sooner or later you will. You cannot simply dump the stuff down the drain. If you have the elbow room and can stand the mess, go ahead with a parts tank and solvent. Otherwise, you'll need a different method.
Instead of the smelly mineral spirits, use Brownells d'Solve. It is a concentrate that you mix with water to make a cleaning solvent. Before you scream that water is the tool of the devil and will not come near your shotgun, consider that we will be using a blow dryer or heat gun to dry the parts, and penetrating lubricant to protect them. Mix your concentrate and scrub the parts in a sink or basin. Once clean, use the blower to dry them and immediately oil them with a penetrating oil to cover the parts and displace any residual water. You can filter the used solvent back into a storage jug, and when it is too nasty, cap the jug and take it off to the nearest landfill or recycling depot.
To scrub the bore you'll need bore solvent. Unlike the general cleaning solvent you will not need gallons of bore solvent. A quart will last you years. Keep the solvent in the bottle clean, and transfer the solvent to your cleaning patch or swab with an eyedropper or a clean patch. Don't just dunk the grubby swab or brush into the bottle, contaminating the solvent in the bottle. Unlike rifles, you will not need abrasive bore cleaning compounds to remove the fouling. The shotgun bore does not get exposed directly to copper as a rifle bore does. The only thing your bore is likely to see is plastic and powder residue. If you shoot slugs or buckshot, then there will be some lead. All of this will come out with a brush and solvent, or in extreme cases with a swab wrapped in brass kitchen cleaning mesh.
Which brings us to lubricants. Rather than petroleum-based lubricants I prefer synthetics. Petroleum-based lubricants are tough on wood. If your shotgun sits in the rack (as most do most of the time) the oils in it will settle in the rear of the receiver and come in contact with the stock. Petroleum products soaking into the wood soften the grain and lead to spongy wood that cracks. Synthetics will settle, but they won't attack the wood. I use Break Free, FP-10 and Rem Oil as light lubricants. For contact surfaces that need a more persistent lubricant, like sear tips and hammer hooks. I use Chip McCormick's Trigger Job. One jar will last a long time, even when you may have a bunch of guns to treat. My jar is so old it dates back to when he called it Trigger Slick, and I have used it on almost every firearm that came through the shop for work or repair in the years since.
Brownells d'Solve is a water-based cleaning solvent. Used in conjunction with a heat gun or blow dryer to evaporate the water, it is a convenient, odorless and non-toxic means of cleaning your shotguns.
Standard solvents and chemicals will do many things, but they won't strip old finish off. Especially the finish on Browning shotguns. Consider the cost of extra supplies if you want to do the job yourself or send it out.
If you are going to go past simple disassembly and cleaning, you'll need more tools. To strike some of the tools you'll need a hammer. A ball peen hammer of a medium weight, 8 to 12 ounces should be enough. For filing, the most useful file I have found is Brownells Swiss pattern, 8-inch extra narrow pillar file, #2 cut. It is large enough that you can get a good hold on it. It is small enough that you can get to places you couldn't with a large file. The #2 cut is a medium-fine cut, but the file can be used to remove large amounts of material and still finish with a smooth surface. The only drawback to the file is its flexibility. You can press on it hard enough to bend it, and if you aren't careful you'll file a rounded cut instead of a flat cut.
If you need a larger, heavier (non-bending) or coarser file, then get an American pattern Mill file, second cut of 8 or 10 inches long. It will be stiff enough that it won't bend, which is also useful as a backer when sanding.
For woodworking, get a cabinetmaker's rasp. The two files I mentioned are too fine for wood, and will fill up with wood after a couple of passes.
Buy as much lubricant as you think you'll need, and then some. You can get quantities from the ⅔ of an ounce to a full gallon.
To keep your files clean and properly cutting, get a file card. The one we're discussing is a flat piece of wood with short brass or bronze bristles used to card or comb the filings out of the teeth of the file. If you don't remove the filings, the file loads up and stops cutting. Before it stops cutting, the partially-loaded file cuts unevenly and makes a mess of the surface you are creating. The rasp will also need regular cleaning to keep your woodwork smooth.
If