i picked up a brake master cylinder reservoir at the junk yard to replace my leaky one in my xj. the reservoir i got from the jy looks pretty dirty on the bottom. my question is, is there a good way to clean out the build up on the bottom of the reservior? i was thinking of taking to the car wash and hose out the gunk, but im not sure if that be good idea to get water in there. how do i get the build up gunk out?

Brake parts cleaner

This is what I used. Works pretty good but it's tough to get everything out.

"the reservoir i got from the jy looks pretty dirty on the bottom"

If it's dirty in the bottom it's dirty throughout so disassemble it and clean it all.