Generally speaking I've used Mr Muscle Oven Cleaner for removing paint off of rolling stock etc (Plastic/Metal) with no ill effects to the models. Just your lungs!   Always a good idea to wear gloves too-Marrigolds or Nitrile ones are best  if going into full PPW mode then a mask and safety glasses would be advisable.

It does tend to work better with enamel finishes lifting them easily. Some factory finishes such as LIMA are quite resiliant to Mr Muscle and may require a second/third attempt. I also tend to put the model in a plastic bag, spray in the Mr Muscle then seal the bag. This tends to soak the model and use less oven cleaner.

See how you get on. If it hasn't worked then there are further options to take.

Cheers,

Mark