I am getting a strat body from Warmoth, but am unsatisfied that they only do poly finishes. I want a thin nitro finish so that it wears down easily and gives the guitar that vintage look.

What would be the best way to thin down the poly finish but make the finish still look normal without scratches or swish marks from something like steel wool?
High as tits
Mr hankey and James are both right. Poly doesn't wear even when it's thin and if you want nitro or if you want something that will wear, you should get an unfinished body and finish it yourself.
Not taking any online orders.
Trust me poly is crazy hard to strip. It took me about 4-5 days to strip the finish from my strat. I finally found this stuff from Klean Strip called Aircraft Striper or something like that and it worked better than anything else I tried. I would just get an unfinished body though.
Custom Strat
Boss BD-2 Blues Driver
Electro Harmonix #1 Echo
Fender Blues Jr.
Crate V18

“America is all about speed. Hot, nasty, bad-ass speed.”
-Eleanor Roosevelt, 1936
This is most heavily worn poly-finished guitar I've ever seen:

It has about 30 years on it of heavy playing. Trout gigs a few hundred times a year, almost exclusively with that guitar.

My point is: poly will wear, but it will take A LOT of playing. A lot.