well i tried to paint my oem front lip with duplicolor and after a while it got chipped and stuff and now i want to repaint it but i want to remove all the old paint. I tried sanding it but not all of the paint will come off. Will paint thinner work on this surface?

 

id just take some smooth sand paper and go over it, then primer it and spray. Don't think you will be getting the OEM paint off.

However u could try brake fluid, its suppose to take paint off like nobodys business.