[devellis]

When I've cleaned old instruments, I start by dusting it off with a soft brush. Make-up brushes are good for this, as they're really soft. You can usually get a set of several for a few bucks in the make-up section of a drug store. Next, I wipe it with a barely-damp, soft cloth (like an old tee shirt). You'd be surprised how much grime that will take off. If it's still dirty, I'll get a fresh, soft cotton cloth and put a little naphtha (e.g., Ronsonol lighter fluid) on it and spot-clean the difficult areas with that. I've used it on a wide variety of finishes and have never had a problem. But if you want to play it safe, you can test it under the truss rod cover or some other inconspicuous place to be sure it doesn't react adversely with the finish. If I want to shine it up, I'll use Virtuoso polish. Again, I've used the stuff on a variety of finishes with no problems. I'm sure there are other polishes that also work well but that's the one I've stuck with.

It may be a good idea to clean the frets while you're at it. If there are no electronics on the instrument, then 0000 steel wool will work well. There are more specialized tools like the polishing erasers that Stew-Mac sells or Micro-Mesh pads, both of which I actually prefer to steel wool because of the latter's residue (which can prove disastrous for any electronics on an instrument). But steel wool will work and is probably easier to get in a local hardware store. If there's a lot of crud adjacent to the frets, a single-edge razor can be used to gently scrape the area between frets to get them clean. Something like Lizard Spit, used very sparingly, can be applied to the fretboard to darken it. A drop or two on a clean cloth should suffice for the entire fingerboard.

I'd never use Armor-All. It's pretty much silicone and once applied, that stuff never comes off and migrates from area to area on a surface. If you ever need a crack repair or a finish touch-up, having applied silicone could make the job go considerably less well.

Less is really more when cleaning an instrument. Start with the gentlest approach involving the most benign ingredients (like clean water). If more is needed, you can gradually increase the strength of what you use. But much more than water and perhaps a little bit of mild detergent is rarely needed. Instruments get dirty from skin contact and air-borne materials, neither of which constitute a difficult clean-up.

Oh, one other tip: As Wade said, it's important to get the bridge in the right place. If you take it off for cleaning, you might want to tape the top and bottom pieces together while they're off the instrument. That way, the top won't get put on backwards. Both pieces should be returned to the instrument in their original orientation, the bottom half of the bridge so that it mates with the top properly and the top half so that the string slots correspond to the strings correctly. When I take off removable bridges, I often pencil a small "B" and "T" on the under-side of each piece to indicate the bass and treble ends, respectively. That way, if they get separated, I can easily determine how they should be oriented on the top. Discovering that small trick has saved me some aggravation over the years.