I would try and not get any on the inside of the pan. You don't want that coming loose and pumping through the engine or clogging the filter. Also don't think mineral spirits or thinner will strip the old paint. You can buy stripper at most parts stores.
POR makes a paint that appears very similar to powder coat and comes in color. The pan needs to be stripped to bare metal and prepped properly and it will last a long time. They even have a paint especially for engines. I used their regular gloss silver on my pan and happy with the results. I have used their black paint on several frames and very happy with the result. They don't call it powder coat in a can for nothing. http://www.por15.com/