When washing the car a used Dobie, or similar gentle scrubber for dishes, works just fine. and, yes, keep some wax on there to make removal easier. Use high beams at night only when needed during that season since they attract more bugs.
Pre-treat with Poorboys Bug Squash at 3:1 (water:concentrate) and let it dwell for 30 secs or so. using a MF bg sponge, it takes bugs right off--no more dealing with petroleum distillate-based stuff.
Sudsy ammonia. Full strength. Alkaline detergents disassemble (unravel) proteins, which is what bug guts are. Cheap and effective. You WILL need to rewax afterwards...