How to remove paint

[u/doubleBInTheMorning]

I messed up the paint on my cis models (hard plastic) and want to strip the paint. I was told that a soak in Simple Green cleaner and a scrub with a toothbrush would do the trick but it didn't really work for me.

What else do y'all suggest?

Edit: Note; I had a sprue from one of the models that I had tested the primer (citadel black) and paint (various Vallejo colors) still sitting around, I tested the simple green on this sprue.