Boiling water will cause flash rusting in the barrel. Cold water, a little soap works great. Boone or Crockett didn't use boiling water, too much trouble to get a fire going just for that.
As far as lube goes IMO Wonder lube is junk.
I have used Hoppes #9 Blackpowder patch lube and cleaner for years. A slightly wet patch in my .45 rock lock and I have not had to clean between shots, all 18-20 of them on average. About 20 shots I clean her and start over.
It's more likely Boone or Crockett had water, hot or cold than they had Hoppes #9! In fact I would bet a £1000 they regularly made fire to boil water!
I don't get " flash rusting" when I use boiling water.
I also don't get (understand) the OCD syndrome like negative attitude towards any surface oxidisation of the steel.
Some on here must lose hours of sleep over it!
Why, I don't even bother cleaning my guns for days if I choose not to.
My barrels once completely heated via boiling water are dry in no time and free of any caustic salts and fats or oils.
Whilst still warm a patch with my bees wax and olive oil coats the bore.
I put it away and forget about it.
Some of the concoctions on here make me often wonder if somehow the firearms have become some kind of veneration idol for individuals!
Its just steel boys, iron. It just likes to absorb a little oxygen.
You only have to remove salts and fats then keep oxygen off it.
Energised water (hot water) is the perfect detergent for salts. So that's the salts gone. Now a little animal fat to keep the oxygen away, job done.
Even instructions to clean early breech loaders that use black powder include a small funnel and a kettle!
I bet some of you never take a bath you sound so petrified about water!