Just wipe the master with Easy-Off oven cleaner. It should soften it up enough to wipe then scrub off most of the Rustoleum. Be sure to drape off everything else.

The Hirsch paint prefers to be baked to cure for durability. I baked my master cylinder bare casting on a rack over the woodstove, but heat lamps or just plain engine heat would likely do the trick. Calipers will provide plenty of heat.