I always use Mr Muscle oven cleaner . Spray it over the plastic model , place it inside an old tupperware box ,seal down the lid and leave it for 24 hour's. I then mix a little bleach with another plastic container of water and gently scub the paint away with an old toothbrush... Be carefull of any small parts that might break off ; I tip the container of dirty water through a strainer to retrieve any small parts ... Works well stripping Humbrol , Model Master enamel paints and Gunze , Tamiya acrylics . Not so good on Holts Dupli-color rattle can paint finishes.