When it comes to any painted surface "scrubbing" is never a good idea. Scrubbing should be kept for the likes of wheel arch linings only pretty much. There are plenty of pre-wash solutions out there that will aid the safe removal of bug splatter, Autofinesse Citrus power is certainly a good place to start as stated by Dave. You should only really need to slightly agitate once left to dwell, if not removed fully simply repeat process until the whole splatter has been broken down and removed.
plus like dave has already touched on, is the car waxed/sealed? If not this is partly the reason for struggling to remove them pesky bugs. A sealed/wax surface will make the splatter a lot harder to stick to thus making the removal of such grime a lot easier and needless to say, a lot safer