Brake cleaner does leave a residue. Don't use it on mountain bike brake discs, for example, as they don't get hot enough to burn off the residue. Car brakes will burn it off no problem.
Hitting the poly with a fairly aggressive solvent like acetone and then letting it evaporate just before the first coat of whatever you're going to hit it with helps soften the surface and let the chemicals of the paint bond with it a little more effectively.
Last edited by OlongJohnson; 06/07/21.
