I'm a bit confused. I associate pin spanners with adjustable cups (RH in both position and threading) . Most LH (read fixed cup) have flats, in my experience. Also good to be sure of thread direction on the fixed side.
Heat from a heat gun can be directed directly on the cup, without effecting the paint unless you are careless and don't heat it too long. The heating cooling cycle can help break the bond.
I'm a big fan of the 50/50 mix of ATF and acetone. Again, paint can be affected, so it needs to be applied carefully and conservatively.
VAR makes the removal wrench with many sizes for fixed cups. This is similar to the Campy tool in that it grips the flats of the cup. Kingsbridge types use only friction, controled by how tight the tool grabs the sides of the cup, and will sometimes slip.
My 2 cents.
Mark Hoffman
New Britain, CT
USA