If you damaged the surface, you need a new screen.
For bugs on a Dalite HP screen or standard matt white screens I use Hydrogen peroxide on the stain and let it sit a while, then rinse with Denatured Alcohol. Always check with the manufacture to see if he screen can be cleaned and follow their instructions first.. If they don't work, then wing it..worst that can happen is you make sure you now have to replace the screen.. who could stand looking at a bug stain anyway??