Many years ago, I had to strip some 'n' gauge rolling stock, so I put some Castrol Girling brake fluid into an empty coffee jar, dropped the bodies in, shook the jar then left it for a couple of days.
After a quick wash down, the bodies were ready for re-painting.
These days, I use a product called Modelstrip which, as far as I can gather, consists of Plaster of Paris mixes with Sodium Hydroxide into a thick paste. Application is simple; using a suitable instrument (and wearing rubber gloves!!!), cover the area to be stripped with the paste, then place it into a polythene bag for 24 hours, so that the paste doesn't dry out. After the allotted time, remove the model from the bag and wash it under a tap. Use an old toothbrush to get into the nooks and crannies. The paint should come away with the slurry. Any paint remaining can be removed by a repeat performance.
Hope this helps
Colin
Gentlemen! You can't fight in here; this is the WAR ROOM!