"So the fitting can turn green from the flux or the flux brush getting burnt from the hot fitting. Then you but it in the flux for the next time and content the flux."
"So the fitting can turn green from the flux or the flux brush getting burnt from the hot fitting. When you PUT the brush back in the flux container, you've CONTAMINATED the flux for the next time you need it."
...Using the brush after heating the joint.... oxidized copper (green) and burned flux getting back into the container... vs only using the flux brush to brush flux on cool, clean copper
this will probably not be your last repair...
you can buy a bag of "plumber's bread" that contain several plugs of dissolving material (various sizes) that will give you a couple minutes of water blocking... AND THIS STUFF NEVER SPOILS
when you turn on the water, if you have a faucet down the line without an aerator (tub) open it up first to blow out your bread residue