It sure is nice to have lots of valve,what a pain to solder with water in the pipes.I have been at a couple houses where there are no shutoff valves at all .
An old plumber's trick:
Obviously if there is standing water in the pipe there's not much you can do about it, such as in a vertical pipe with no way to drain it, but in other situations such as a horizontal pipe that has a seeping valve closer to the supply or water trickling from it there is a way to temporarily stop the flow long enough to sweat the fitting: Get a piece of white bread (that's right--bread) and stuff it into the pipe, pack it in good and push it up the pipe as far as you can. After sweating the fittings and turning the water back on open the water line and stand back. the bread plug usually blows out with quite a bit of force.
If a faucet is at the end of the line, remove the aerator first.
I've done this and it works. Stay away from the multi-grain stuff, doesn't work as well.