Have to agree with that wooden mallet philosophy.......mine:
One regular use is unseating freewheels on my bike. With a long combination wrench and a good snap with the mallet, even the impossible ones come loose.
If you have dirty threads that need cleaning and they are difficult to reach, make up some thread chasers like these:
Just regular nuts of the appropriate thread size with a few saw cuts added. Places like "J" bolts on gas tanks and shock absorber studs come to mind. Try to tighten the nut first, a couple of turns, so you can get right close with your chaser. Be liberal with the oil ahead of time.
To reach some of those gas tank nuts, I made up an extended reach socket (9/16" in my case).
An old socket, piece of pipe and a 1/2" coupling nut welded together.
I usually change the nuts on the gas tank bolts to 1/2 of a coupling nut with saw cuts on both sides, so it can clean in both directions.
Another place I installed those saw cuts was on an old table saw. Both the tilt and the up/down adjustments had room to do that. No longer did the nut try to ride up on top of the sawdust in the threads, and with a bit of candle wax both adjustments operated like new.