Like said above, cut and buff using automotive materials. By the time they are bad most of the UV protection is gone that’s why they go to s*** worse each time. The only way I’ve had good long term luck is to sand them down heavy then leave in 1000grt, adhesion promote and use a automotive clear coat over. That gets the UTV protection back and they’ll last a long time after that. Cleared over lots of sets, works great.