People who say that their lens has a grime or dirt they cannot get rid of ,have an abrasion problem ,not defined scratches but millions of micro scratches that make acrylic go cloudy,When you polish it it will seem to get worse then with more polishing it goes clear as you abrade the top coat.
when model making at work we have to polish the cut ends to make them clear again,Brasso works for me ,but may be a little harsh for this.
You may be better of with Applesauce scratch remover ,designed for Ipod screens pre glass