The coating is varnish, it should come off with acetone. Take your time.
I know of people who have submerged it in acetone for an hour, and it just dissolves (I would not try that).
I tried the resoldering technique, but it did not work for me. I ended up buying a used amplifier (it worked right from the get go)
1999 Porsche 996 Carrera Convertible
1994 420E - SOLD
1986 300E - SOLD, what a car