Toluel or Toluene is my preferred solvent, Xylene is a close second. Add 25% IPA to slow down its evaporation. Soak it, leave it outside if you can for a day as its extremely flammable (vapors too) then wipe and plastic brush away. Wear heavy rubber solvent gloves that go up to your elbows, and a good pair of safety glasses, and plenty of ventilation.
You can get Toluel at most commercial paint stores in California, so it should be more available anywhere else.
1967 Mercury Cyclone GT Convertible, 390 FE