Traditional 'bug/tar cleaners' work OK, but they seem to work best when you are just dealing with one really big stubborn baked-on bug. For 'mass impacts,' it seems like more trouble than it's worth, IMO. When it's really bad, I do it this way: When I wash my car (which will be every day when lovebug season starts...) I keep the front bumper constantly wet while I'm working on the rest of the car. I'll intermittently wash it, using the 'bug scrubbing' side of my sponge. (In fact, I have a separate one just for lovebug season.) It's a net-like weave that won't scratch the paint. That usually gets the job done to the point where I can use some 'quick detailer' to remove the smudgy traces.
If they are really bad, I'll soak a towel and lay it on the hood and bumper, to just soak-in for a while before I even start washing. (I give it a good rinse, first.) If it's super dense, I'll wet it and then put a coat of car wash right on it. Then I do as above. When I'm done washing, I will often re-wax the front edges again when it was that intense.
Last year the lovebugs were so bad after just one 50 mile rural drive the flat edge of the bumper looked like it was covered with black suede.
