For those not lucky enough to have a source of braided wire at sensible prices one possible solution is to get hold of de-soldering braid which pretty cheap, and with care can be opened out into a tube (most of the small braids I've seen are actually flattened tubes) and, with care and possible lubrication with vernacular English, one can get un-braided wire to feed into the braid tube. You can then proceed as Simon describes in his posts about using braided wire.
I agree everyone else that shielding the wire is about the practical way of shielding the wiring of ES style guitars. The one suggestion I haven't seen already is to use relatively heavy gauge, single strand braded wire. I am not sure what gauge I used, but the single strand was about the largest size that would fit through the eyelet on my pots. The single strand wire will hold it's shape somewhat, and that enabled me get the pots and jack more easily positioned after getting the #$%@^& thing through the F-hole.
...It's a PITA to use, and it's not really cheaper than braded wire. IMHO it's only worthwhile using the a wire sleeve if you are running different colored wires, or a bunch of wires from one place to another in an ES style build. Even then, the one time I have done it I kept thinking "there must be a better way to do this."