I’ve been using acrylic paint for over 35 years, and it doesn’t stick very well to plastic. On the lenses of your sunglasses, try your thumbnail, or the end of a Popsicle stick. Be careful if the lenses are plastic. A product called Goo Gone says it removes dried acrylic paint, but the fumes from it are INTENSE :o and can give you a whopper headache. Use it outdoors if possible. I don’t know if it eats plastic since I’ve never used it for that. But I recently got lots of little drops on the plastic face of my wristwatch while painting (with latex) and just smoiked them off with my thumbnail. Good luck!!