I found two places that I was constantly getting dirty/wet. I installed a large tub behind my front hood and find that when in rain or washing the coach, the tub lid gets full of water and dirt. The water is coming through the opening at the top of the hood and front cap opening. Even though most don't have a tub behind the hood, it's probably not the best thing to keep splashing unnecessary water on the generator and jacks pump.
I just added some foam door insulation along the top edge of the front cap opening. When I close the hood it presses up against the foam. It's hard to distinguish the foam because it's the same color as the paint.
On my coach, the last bay on the passenger side has the two starting batteries, fuse panel and battery disconnect. Every time I was the coach, I open that bay the batteries, connections and some items I store in there are covered in road debris.
The lower section of the bay is wide open and you can see the DPF portion of the exhaust system. I didn't entirely close up the lower section since this bay has batteries. Since I had removed my plastic mud flap and replaced it with rubber, I used a piece of the flap to prevent the debris from entering the bay.
Simple mods, but hopefully will keep some parts cleaner.