My buddies and I have used Herculiner on 4WD's in the past, it works real well for that. It is very durable and rough. It does scratch or rub off against rocks and stuff but that was pretty hard use.
It is very messy to put on but easy. Just tape everything off real well first and clean the surface prior to applying as per the insructions.
For the price and the do it at home ease, I think it is good stuff.