Fixing up my old house I learned a few things.

1. Replace your propane torch with the map gas (yellow bottle) torch. It burn hotter and will evaporate the drops of water faster or put more heat into what your soldering to help make up for what the water is sinking away.

2. Bread works. Cut the pipe and after the most of it quits draining stuff some bread into it to plug it for a short time, enough to solder your joint. Then you turn the water back on the breag gets soggy and washes away.

3. Always buy the bulk contractor bags of parts, elbows, t's etc, never know when you may need one.