Joe,
see my answers below in your text.
1) Do you guys level the frets and dress the ends before or after the neck is attached and before or after the finish?
I install the frets beforehand but do all fret work after the neck is attached and the finish is done.2) Do you guys cut and install the nut before or after the finish?
After (do you partially finish over the nut end like gibson?)
No3) Do you guys drill all the holes for tuners
yes, endpins
yes, stap buttons
no and tail pieces before or after the finish?
4) for raised pickguards, do you make and install the hardware before finish to check for fit?
Never used a raised pick guardAnd last but not least: Any reason to really string up a guitar in the "white"?
Some guys do because they can "tweak" things before the finish goes on. I, however, choose not to string up in the white but rather in the buff. Being a fair skinned Irish boy I guess you could say I do string up in the white!