Those types of trailers normally clean up easily. A medium foam pad should be all you need. You will need a fair amount of pads depending on trailer size. If...
OP, have you ever tried removing carpet from the car and pressure washing it to clean it instead of repeatedly extracting the carpet? Or just put in new carpet...
Just use the Brown royal and clean them just like you would regular factory wheels. Yes you can use regular car wax or sealant to make them easier to clean in the future...