I got around to some guitar work recently. I bought a Fret Levelling Beam recently (more about that in a mo) and used that on two Telecaster kits I built a while ago where there were some fret issues, largely no doubt to me bodging it before with a shorter file. The Levelling Beam did seem to make it a lot easier to get something considerably better.
I also have been installing some shims on the necks of various guitars. I know there is a lot said where people groan etc about them but if you've a bolt on neck it actually is one advantage that installing one is a non-destructive way to try and sort stuff out. In particular, with my 12 string electric it helped me get a better action and massively improved overall intonation. On one of the Telecasters it helped get a better angle over the brass bridge saddles.
Finally on the Squier that I rebuilt sometime ago it helped set a better working angle on the bridge again allowing palm muting to be much less of a painful hassle due to the adjustment screws. To my ears I heard no discernible change in tone. I did buy some thin maple veneer, about 1 mm thick so there is good wood to wood contact maintained, maybe plastic shims or cardboard (yes I've used that before!) are reasons why these get bad press.
Here's a quick photo of the Squier Strat in bits, the veneer is about to be cut to fit... It is by the pencil which I've just drawn around the heel of the neck onto it.