If your lapping the cpu, or the heatsink, and you want to use a liquid (to keep the dust down) then I would recommend using something oil based like WD-40. But remember to clean it up with alcohol or lacquer thinner afterwards.
Unless your working in socks and rubbing your feet in the carpet static really shouldn't be a problem. Just ground yourself before you start working (grab something metal).
Unless your having heat issues, or your just wanting to be the Ultimate Overclocker, lapping your cpu is not practical for most users. But if your wanting to squeeze every last MHz out of your cpu then lapping it will help.
The biggest problem you might have when painting a fan is applying the paint unevenly causing the fan to be out of balanced. I paint my fans while they're spinning.