The silver solder I've seen done was using acetylene plumbers setup. I'm not even sure a MAPP gas would get hot enough to do a good job.
I think I'd be looking at finding a tig to do it. I cant believe how cheap these have become and how useful they are.
Having an argon cylinder isn't cheap in addition to the rest of the filler, ppe and the machine itself, but I watched welding tips n tricks Jody hard face a chipping hammer with a drill bit. How cool is that?