Been there and done that more than once.
First power wash the outside and get the wheel wells real good until the mud and debris stops dripping onto the tires and wheels. Then lift the hood and spray all the mud that was dripping off the inside of the hood and then the entire engine bay. Underneith, power spray everywhere, especially the brakes and nooks and crannies everywhere. Rip out the mud and grass and sticks and stones that are dripping and drooling everywhere underneith. Get a garden trowl and scoop the mud and debris out of the skids. Keep scooping using your trowl, hands, and a big ugly screwdriver if necessary. Spray it all again. Spray it all again. Maybe a third spray if necessary. make sure you get it all out of the inside of the wheels so you don't get death wobble from unbalanced wheels. Double check breather lines for diff's, tranny etc to make sure they are still attached etc, wireing etc. Check fluids. Check everything underneith again. Take a shower. Drink a six-pak and relax.
Two weeks later you will still have dried mud caked and baked on under the jeep in places. As time passes it will dry and fall out all over the road every time you hit a bump. No one will tail-gate you.
Don't do that again......unless you are stupid like me......haha
War Veterans Jeep Group #31
Black Jeep Society #217