I would advise using a blank. I would of course be wearing eye and ear protection, watching from a thousand yards with binoculars, and preparing to chuckle maniacally if the gun blows up.
In all the threads like this at THR, there's always a closet arsonist recommending that you use an open flame of some kind to loosen things up or something. I don't know if that works, but it too appeals to my destructive nature. If you still want to live dangerously and none of the previous methods worked, you could probably dump some drano down the bore. I think it would dissolve the patches. Heaven knows what it would do to the bore, though.