I can't answer all your questions but try on some.
I use heat gun because I had it,tried candle and didn't like.
Curved tip forcips work for me clamp over hook eye help keep paint out.
2in cup for me. Build one and could always modify to 3 if necessary.
No reason to add clear to a standard color that I know of.
I heat,paint,then clean paint from around eye then bake. You don't have to bake but paint will chip off eventually with out it.
Make a rack out of a coat hanger I just bent 2 90degree bends twisted a eye in each end and screwed to a scrap board.
Paint will not harden in air.
Fatman and some of the other guys will get on here some suggestions who beter versed in this than I am.