Flush, flush, flush, remember at some point in the flushing process to open the bypass valves to the water heater. I like to flush the lines at least a minute or so before opening the bypass valves to the water heater to minimize any antifreeze entering the water heater as there is a large volume of space to try to rinse if you get a lot in there. I also open the water hater drain valve during the flushing process to help flow more water through the tank.
I also recommend every spring to sanitize the FW tank and lines.
As for the breaker, it could be the water heater, the owners manual will tell you what breaker is for what. I labeled all of mine. I do turn my water heater breaker off, so we do not accidently turn on the water heater when no water is in the tank. If you do accidently turn on the heater element with no water in the tank you will fry it. the breaker is only for the electric heat option, not for running on propane.