They don't tell you what the stuff is, but Easy-Off Oven Cleaner is what most of us use. As Dave says, anything that strong CANNOT be allowed to get on the paint. I'd pull the windows myself and do this on a stand even if you don't remove the trim from the rubber. The rubber and the glass are not affected by the caustic solution. But, you don't want to leave any in the rubber grooves either. This way, you could hose them off real well before polishing. I removed black paint from a rear window trim and polished it on the car. I ended up taking the glass out (for another reason) and then polished the trim separate from the glass/ rubber. Much easier. If you take the glass out first and then remove the rubber carefully, the only problem you face is threading it back into the rubber. If you're careful with it, it won't deform or bend out of shape and will reinstall easily. Or, you could flip a hundred on a glass installer to do both if you are there to provide some assistance. That is unless the subject car is a Targa. If that's the case,
nevermind.
Removing the trim out of a door is a lot of work. I'm not disagreeing with Dave here, just thinking about something different. How about pulling the hinge pins and laying the doors on a stand, too. That way, you won't be fighting gravity and your nice paint job below.