software

Couldnt I just put copper or aluminum tape inside the control cavity?

Yes that what I do, but like the paint get your multimeter out and make sure you hav connectivity between all the pieces.

Yes, you can. It's just a little easier to get the paint in the corners and stuff. You'll want to make sure there's an electrical connection between the pieces of tape, though. Usually the sticky side isn't conductive.

Shielding is preferable to copper or alu.
That way you can get it all covered.

I have been told that shielding, paint or tape, has little or no effect unless you are in a VERY noisy environment (maybe your rehearsal space is full of Tesla coils and Van Den Graf machines or something). Can anyone confirm or deny this?

My Strat's cavity is shielded, and my Tele's is not. I don't think one is noisier than the other.

I've heard no audible difference between aluminum tape and no sheilding at all. I think it's got to be due to the tape's adhesive not being conductive.

fold over the end of the aluminum tape so you have metal to metal contact between sections. Also remember your pickups stick up out of the pickguard where they aren't shielded (unless you shield the inside of the pup covers) and are susceptible to noise.

I have always used paint myself. It is just easier to get right.