What kind of main shutoff valve do you have coming into your house? Sometimes older gate valves can be a cantankerous sort either not shutting off all the way, not turning back on after being shut off, etc.
The bread idea is an old one I've seen people use in the past. Just be sure to take the airators off all your faucets and run alot of water through to clear it out. I dont use bread as a rule unless I'm making a sandwich. There is an item on the market that looks like a big vitamin E pill. I cant remember the brand name, we just call them "beads". Two sizes, 1/2" and 3/4". Shove one of these in the pipe, solder away, add heat to the pipe where the bead is and it dissolves. I've successfully used the beads a handful of times though ideally I'd rather see if I can get the water out of the line and not shove anything into it to accomplish this.
Another way to stop the water is with a JetSweat and ballvalve though now you're talking bigger money. I don't think a DIY'er would really want to invest that much into a JetSweat kit that might be used once in a blue moon.