High pressure hose as much off as your can. Get 2 buckets, 1 with meguirs gold class in it and another with just water. Dip in the meguirs and start cleaning, when you get the sponge dirty, rinse it in the clean bucket of water to stop you putting dirt and stuff in the meguirs detergent as you dont want to be scratching your car. Empty out the clean/dirty water bucket and refill regularly. If you want to go one step further if you find there is still stubborn marks on the car. Buy some detailer clay, its about $50 a bar but works a treat!