99% Iso Propyl Alchohol will take acrylic down to the plastic Guy without damaging the surfaces - not sure about the enamel though so maybe test on an undersurface first?
I have used with complete success the Mr Muscle oven cleaner 'treatment' before - put parts in large sealable poly bag, spray in a copious amount of oven cleaner, seal bag and leave overnight. Wash parts under a tap following day. Resurected previously painted parts for a 1/48 Helldiver quite recently - all back to like new overnight. The parts had been painted a long time before I got it and were probably painted with Humbrol but can't be ceratin - again you really need to do a test.
Hope that helps a little more
Tug