Now see if you lived in Mississippi you could cover a dead goat with grease and wash it at the local car wash with no problem. As a matter of fact someone would probably try to talk you out of the goat. I like the idea of putting down one of those synthetic fiber blankets the wal mart kind. Maybe put some on the ground and tape some plastic around the bottom of the truck to keep down the over spray. You could also dam up the drain with some screen and use sand on the uphill side as a filter. When I was a kid you could polish a dime with mercury, squeeze lead shot on your fishing line with your teeth and ride in the back window of a 57 Chevy while your parents smoked a carton of Viceroys.
Neil