Okay so I've been learning a lot about what not to do to a bass guitar!!
I started out with a Squier Precision Bass, the cheapest of the cheap. I'd bought it from a friend for fifty bucks, and it had a few initials scratched into the paint here and there. It was black, but I've always wanted a natural wood bass guitar, so I decided to get creative and try to make one for myself.
I started by removing every nut and bolt from the body, including the bolt-on neck and all the hardware. Everything gets deposited in a tupperware container. I cleaned all the hardware by hand with a microfiber cloth and some patience, save for the screws, most of which are filthy or rusty and I'm looking into options to get those spick and span as well.
I started the DIY part with the pick-guard. I sanded it down with 180 grit emery cloth to get the surface roughed up for painting, then coated it in three layers of latex-based chalkboard paint. It looks great, and definitely won't hold up to repeated pick scrapes, but that wasn't really the point. When the paint had dried, I used a file to remove the excess paint from the edges of the guard, especially around the pickup slots where things need to be pretty precision.
Next came the neck. I taped down the rosewood with painter's tape, then used #0000 superfine steel wool to polish the frets. This was shit work, and I got steel wool everywhere. Next I took off the tape and cleaned the entire neck with another microfiber cloth and the edge of a credit card to get into grime-packed areas. Lastly, I rubbed some lemon oil into the fretboard and let it sit for twenty minutes or so before removing it.
With the fretboard clean and prepared, I moved onto the headstock. I used more superfine steel wool to combat the ugly Squier headstock decal (which on Squiers is silkscreened on; don't try this on high-end gear as the imprint is buried into the wood and you'll never get a clean finish). I couldn't quite get the afterimage off of the headstock, so I took to it with 180 grit sandpaper and carefully sanded away until the decal was a thing of the past.
On to the body. This was a royal pain in the ass. I'd heard of people using chemical paint stripper to get rid of the stupidly thick lacquer coats on bass guitars, but I didn't trust it and instead bought a palm sander and various strengths of sandpaper. I started with 100 but realized immediately it wasn't rough enough, so upgraded to 50 grit and took to the project. It took me 3 or 4 hours to get through the lacquer on the front and back of the bass, and another 3 for the sides and horns. From there, I downgraded to 120 grit and did a finishing job with the palm sander and sanding sponges, making sure everything was even and, most importantly, smooth.
I read a lot into different kinds of varnish and finishes, but there didn't seem to be a definitive verdict on what to use and how much of it would be best. I ended up going with Formby's Low Gloss Tung Oil Finish, which is basically a very diluted varnish finish. I only added three thin coats over the bass, which I'm hoping is just enough to give the guitar back some of the tone I took away when I removed the paint finish. Only time'll tell if the varnish was the right way to go, as it's currently curing in my work's garage. Pics to follow!