Usually I just use plain water to wash a snake, but my snakes don't get into motor oil/grease either. If water doesn't work, you can add a few drops of dawn to water then mix it and use that on a washrag, being careful not to get it on his head. Rinse well. Any scuffs and scratches will likely disappear with a shed or two.

If he had open wounds, keep him on clean paper towels or paper, and I would bathe in betadine type cleanser(diluted, and none on head, etc). Do not use any neosporin type ointment that has "pain relief" in it.