My very favorite method of removing old model paint is using SUPER CLEAN cleaner.  Available in automotive departments as a degreaser.  Usually sold in purple one gallon jugs.  There are sometimes store brands of this stuff but I only use the main brand of SUPER CLEAN.  It used to have Castrol Super Clean on the bottle but it is just Super Clean now.  I use a standard paint tray and fill it full with the SUPER CLEAN.  Then place the items in make sure they are completely covered. I do test each item by watching for a few minutes to see if the plastic starts to melt or distort.  I have done this with several dozen old models and have had no problems.  The only ones I have any problem are the early promo models prior 1964.  A very careful eye must be used on those.  It will remove chrome,( be sure to remove any chrome items that you wish to remain chromed) vinyl tire paint, decals safely.  If the model has had several layers of paint on it, it will take extra time to remove each layer.  I had one that had five layers of brush paint on it.  Flat colors can be difficult to remove completely and will very likely leave a stain.  It is amazing how it will disolve the paint and leave most plastics a nice as when it left the mold.  Soaking time can vary but usually overnight will do just fine. Be sure to wear rubber gloves when you have your hands in the solution. An old toothbrush will help get into the tiny cracks and details.  I also soak the clear window assembly. It will sparkle.  DO NOT use on any Hubley kit window assembly.  Rinse throughly in warm water.  On promo models, I remove all the chrome and wash it in mild warm water very carefully using a rensing motion and Q Tips, I clean the rest of the model in a solution of JOY dishwashing liquid and the more soiled with Dawn.  Q TIPS are good for those small tight places.  I have used these methods for past several years with wonderful results.  This is also good for removing paint on tin toys also.