The secret to keeping the front of your motorhome with a 3M mask or without is to clean it on the days you are traveling. The first thing you should do, after setting up camp is wash the front of the RV and the windshield. The bugs are fresh and will wash right off.
If you leave them for a few days to bake on the finish they will be very difficult to get off and sometimes if left long enough they will burn into your finish and be a permanent mark. I learned this the hard way.
Our motorhome does not have a mask, is 12 years old and the front still looks new.
In the old days before I learned the secret, I would have to use rubbing compound to get the old stained bugs off.
If you have a 3 M mask and have stained bugs on it, they will buff off with rubbing compound but they may still leave marks on the shiny surface if they have been there a long time.
A friend of mine bought a a used Mountain Aire with the mask and it wasn't cared for. I tried to restore it with my buffer and it looked twice as good but not new because of the poc marks left by the burnt in bugs.
The secret to keeping it new looking is to clean it daily after use. This way the sun will not cook them into your surface