I don't do off road but my roads are pretty much torn up asphalt. When I notice my chain getting cruddy I know its time for the hose. I've got a method that I like and it works well for me.

I brush off heavy dirt then hit it with a high pressure garden hose after spraying selected spots with "Scrub Bubbles". After a good rinse I crank up the leaf blower and blow it partially dry. Then I spray the entire bicycle with "ArmorAll" tire foam. After that I wipe all the foam off starting with the front wheel. Its during the wipe off that I find anything loose or worn. After dry I lube the chain and spot grease other areas.

My Dad told me any boy with a dirty bike has got dirty shorts. I have found this to be mostly true. Especially after a wet ride... Ha