Yeah, mud is mud. Don't think theres a magic bottle of anything (although it would ne nice) to keep it from sticking to the under carriage. Consider this, mud stains wont just rinse off your hood and its a finished surface with a clear coat seal, so it definitely will not just rinse from underneath. Most parts underneath are porous so it just sticks and sticks. Best solution I have found is the Blech White amd a pressure washer. I am like you, I want my rig to be as clean as possible, and as fun as mud is its a booger to clean, not to mention various mechanical issues it can cause.