for plugging the bore the hardware stores have a thing (can't think of the actual name) that is basically a rubber stopper with a bolt for a core and a metal washer on each end. Tighteneing the bolt conpresses the rubber enlarging its diameter forming a liquid proof seal.
I vouch for the Wipeout though as it is much easier. I have a rifle with a nasty bore and giving it 2 1/2hr treatment of wipeout made it shine. It is still pitted, but it got the crud out of the pits!
It's not a big surprise to feel your temperature rise
You've gotta get your redline fever 'Cause there is just one cure that they know for sure You just become a heavy metal believer.