Its an interesting subject because Motorhomes are pretty bad at getting off the wet stuff.
The biggest joke item has to be the
rolly mats made by Fiamma. I'd like to see the Joker who thought them up try them.
The best stuff has to be Perforated Steel Plate-PSP but it is very heavy. There is now an aluminium version but you could probably have a month in Spain for the cost of the stuff

Something that does work and does not take up very much space are
bread trays.
You will need 4 of them. Cut the sides off and then place them so that the ridged sides are facing out (for grip) Get a jumbo economy pack of zip-ties and join them together.
When you are going somewhere silly, stop and have a look first. Put the mats down and drive onto them. They can make the difference between having to stay an extra day or not.