Rodent proof

They will make a bed in fiberglass insulation. Spray foam does well. (Great Stuff). Truth is, the best thing to do is wait for a cold windy day, heat the coach up and feel for drafts. Most modern motorhomes resemble Swiss Cheese. While you can find some holes, many holes are impossible to discover without feeling for a cold draft. My dad had sprayed his coach, everywhere he could find any leaks. They visited my house over T-giving when it was cold outside, and we emptied a second spray can of foam, just finding all the holes he missed earlier.

And so you can use it again and again without rust streaks, get the Stainless Steel Wool.

Don't forget about slide out linkage holes, if you have them.
I've heard steel wool.
Pat