I will first and foremost admit I have the least experience on here... But I will share what I have.
As far as house paint goes, I've had success with Goo gone. However, a friend of mine says he can't get it to do a thing. But it's not going to really harm anything so I say give it a go.
I use a lot and let it soak in. I reapply it constantly. I recommend a flathead screw driver. Not to go over and gouge the whole thing, but i pick a discreet spot and spin the edge of the screw driver until I dig about a pencil lead sized hole through the top layer of paint. Then the goo gone will soak up under it for a few minutes. If it goes the way it's been working for me, the goo gone seeps in and breaks that bond of the house paint. I then very delicately with the flathead scrape the layers off. Literally I probably get an inch an hour. It gets easier if you soak overnight too. Usually there are two layers, the top latex layer, and whatever pigment on the bottom.. The latex peels off easiest first, and the pigment needs some more gentle pressure to rub it off.
Attached is a photo of the white house paint im trying to remove. The bare metal was there to start with, so don't think this process caused it.
You can see the house paint, the pigment, and then the original paint.
That being said, I've seen some stunning revival jobs on here that may be waaaaay faster and better than this...but this is my two cents.