Whenever I need to strip models of their paint, I use an engine degreaser called Purple Power. I pick it up in the automotive section at Wal-Mart, and it usually strips the paint off of my models within a few hours. I have left resin, plastic, and metal models in it for days on accident before, and no matter the amount of time it did no damage to the models. It really is the end all be all for me.
That being said, it does very little to X-Wing models.
I have soaked my Scum and Villany fleet in the stuff for two days, and a few colors come off, as do certain seemingly random parts of paint from the ships, but a large majority of the paint only sees a mild fading effect. I'm just going to go forward with the project at this point, since I don't think that anything that is still on is going to effect the final outcome much, but it's really frustrating to see two days of waiting amount to almost nothing. As I get them started, I'll be sure to post pictures.