Similar problems as had by under-slung rear calipers with blind holes (I.e. bandit 600) - drilling a small hole from behind and punching it out will do it (as small as possible - half the diameter of the pin max) and once out I recommend filling that hole with something like araldite rapid so as you keep the filth out. You can use silicone sealant, and pop a very small, short self-tapper in.
The Plus Gas method is good, as is the heat, don't cook the seals, though. Brake Fluid will probably need a change if the caliper is heated much.