How can I remove Sharpie marker ink?

I'm back again seeking your help. I managed to recover Cole and Jay's OG hair after a lot of acetone and prying it off with a utility knife (I glued them to some heads a long time ago). Now I just need to finish cleaning the marker ink from Zane's OG hair (silver marker) and Lloyd's (black marker). I tried scrubbing with a little acetone and rubbing alcohol (the kind used for wounds; I'm only going to buy isopropyl alcohol today), but that was the best I could do. Should I leave them soaking...