Simple Green Not Working

Hello! I'm trying to strip the paint from a few of my models. I tried 99% isopropyl alcohol for 24 hours and then simple green for two days. Neither of these have stripped the paint even when scrubbing with a toothbrush. What am I doing wrong? I painted them with vallejo acrylic paints.

Edit: In case anyone finds this post in the future. The answer was a stiff brush. The toothbrush i was trying to scrub with wasn't hefty enough. I bought a sure grips stiff brush and pulled the paint off easily.