With the master cyl. cap loose not off and bleeder slightly open with a
hose on it leading to a container, take a 'turkey baster' or sme such
device and remove some of the old brake fluid. If you do not do you may
put presure on the piston (with a c-clamp) and when piston gives way
(breaks free of the built up crud) forces blake fluid back up to the
master cyl. and you have a mess that will remove paint.