In the winter with all the salt, I'll check the weather and if nothing is coming in for a few days and it gets above freezing, then I use one of those brushes that hooks to a hose. Water comes out of the brush and I go over the whole car. Then I put on a sprayer and clean off the fender wells and underneath. I can do it all in about 10 minutes. Then I just drive it on the highway for another 10 and I'm done.