Collection Points for Mud and Other Stuff

Sorry, but another newb question. I spent a couple of hours de-funking last summer/fall fishing/hunting muck from my lower fender wells on my GM yesterday. So what are the bad collection points for sand, dirt and other muck on 4r? Going to keep it for a looong time and want to stave off rust outs if possible on the body.

 

I spray out the odd little cubby spaces behind the rear wheels each time I wash.

 

Inside of the frame. It's a big pain to clean but well worth it.

Also, inside of the doors. At the bottom of the door, you can see little drain holes (when the door is open) make sure those are clean of debris.