Washing an elephant

It turns out washing a school bus that's been sitting out all winter is not as simple as I thought. First, I turned the kids (8 and 11) loose on it. The bottom four feet are pretty clean on one side now. Then, I got a ladder and started scrubbing the parts of the top I could reach. It works, but it seems like there should be a better way. I also sprayed some automotive primer on some test sections to see how bumper stickers adhere.