I still haven't started soldering, but I have read in more than one
space that putting bread without the crust down in the pipe will
eliminate the chance of steam.


As much as steam can be a problem, lots of standing water in a vertical
copper pipe will act as a heat sink, and keep the joint from getting hot
enough for the solder to stick. You'll know if you are going to have this
problem when you solder your pipe.
You may have to remove more of the standing water.

The bread trick is good for drying that area around the joint you are
soldering, and for holding back a little water seepage if you have a bad
shutoff valve that lets a trickle of water pass thru.

Dave