Ladies and gentlebugs, I finally found some free time in-between university exams, work shifts and studio time and decided to give my first bass a proper layer of shielding. This puppy's been with me for four years now, and while it's a very playable bass, I felt several upgrades are in order. As is obvious from the images, it's a P/J bass, made from the finest plywood, with V/S/T controls - and I actually quite like the switching mechanism in this case.
The first upgrade I planned for it is shielding the interior with copper foil - the rear pickup is a true single-coil and it's very susceptible to picking up 50 Hz (+ harmonics) power grid noise, and the bass as a whole tends to pick up miscellaneous hum (notably from my laptop's power-supply). The hum simply has to go. Now, considering one of the next upgrades will include routing the jazz coil for a dual-jazz (expanding it towards the neck) it might seem a bit redundant - but it's good practice anyway, as I will do the same for my other basses soon enough.
All images made clickable so the monitor doesn't explode from the full-res images until you want it to. 
Pardon the digital grain, the camera was set for a high ISO rating as the lighting was somewhat troublesome for the CCD sensor, but good enough for work and soldering.
So here's the patient:
I supported the bass so it wouldn't scrape against the surface of the work desk. The headstock was planted on a stereo output jack package foam, the body on a coil of window insulation tape. Proved to be a very good idea as it kept the bass stable, easy to move and rotate about, and what little residue it left on the bass was easily wiped off with a damp cloth.
Off came the strings, the pickguard and the bridge. It's very nice to know that even though the bass is a cheaper clone, the craftsmen thought of the bridge grounding. It's attached to the casing of the volume pot, and though the soldering isn't all that great, it doesn't ever cut out, so I simply slipped the wire out of its routed channel. The Jazz leads proved more troublesome as the channel wasn't top-routed and there was no way in hell to get the wires out without desoldering. Thus, they were removed from their positions (one of the corners of the switch and the back of the volume pot).
The bass is as empty as can be now, nothing left inside the body. The thin copper foil was at hand, and I wanted to go with as few individual pieces as possible so I could solder the whole batch together - I'm not sure if the foil adhesive was conductive and I wasn't going to leave it up to chance. I first went with the P-cavity, then onto the electronics cavity.
Layer by layer and the shielding grew in size. The Jazz coil was a bit specific due to the shape, so I went with a different layout.
Two strips vertically and the rest taped horizontally. Very easy and worked like a charm as far as following the contours of the cavity went.
Finally, for a little extra, I went with this:
To ensure the shielding actually grounds somewhere, I made a "bounding box" around the pickups on the pickguard and (later) added a thin copper tape strip from the P-cavity to the pickguard. As chance would have it, the strip crossed paths with a pickguard screw, so I fastened it down properly and that pretty much closed the ground plane.
Unfortunately at this point I forgot to take any pictures, but wrapping up included tack-soldering the points between the strips (again, to ensure continuity) which wasn't a problem because the strip boundaries, though overlapping, were very visible. After that I reinstalled the pickups, bridge ground wire and the bridge itself, botching up the switch soldering once and resoldering after I remembered where the Jazz signal lead was supposed to go.
The Jazz ground lead couldn't stretch to the vol pot casing anymore (possibly because of a tangled wire someplace) so I just resoldered it to the tone pot casing - as many people said before, there's no way to create a significant ground loop inside a bass, so this will have to do instead of true star grounding - when the time is right I'll redo all the wires anyway.
Finally, the bass was reassembled, restringed (with a note to get new strings) and plugged in. Again, unfortunately, I took no sound samples, but I'm certain the bass is now dead silent, no hum, no crackles and the Jazz coil is rightfully singing now, hum-free even when left on its own.
