Advice on removing paint from plastic panels

Hey FABO I got these interior plastic pieces off a 72 Duster I found at a PicknPull. I know, I was surprised, I pulled everything of her I could carry! Anyway, I want to dye these black, as I was giving them a good scrubbing with a green pad and some mild detergent I noticed that these seem like they have second coat of paint on them. As you can see in the pics where there's two shades of blue. On the A-Pillar trim its pretty grainy and comes off almost powdery...

I scrubbed them for quite some time and I've only got about 30% of the bad paint off. Anyone ever have to deal with this and do you have suggestions on what can be used to efficiently revove that coat of paint and not damage the pieces any further?

I know if it doesn't come off anything I do over it won't stick. :banghead: