Another thing to consider is that the paradigm with oxy is that it is so hot, you have to keep the flame moving, and you will have the heat you need the second you hit a small part, like a rack, and you can move it around, and the flame is carborating, and moving it around you can pull filler where you want to steer it. It is hard to get all that happening, and keep the flux nice with propane.

My thought on all that with MAPP and propane is that, it does not work. A better idea might be to hit all sides at once get them to temp and then fire in the silver and quit. This means multiple heads. There are two headed torches, but probably easier is just two tocrhes. Third hand deal. This is how the factories do it with propane.