Why don't you skin them right there on the spot, then put the hides in plastic bags and transport them that way? Why wash them before skinning or wait to skin them once you're at a motel?
Once you have some pelts in a trash bag, spray with raid all you want. To avoid the use of raid I have used soapy water, and adding baking soda and even salt helps even more. It has worked just as well as raid for me, without the nasty fumes. It also washes the blood off the pelts and the salt/baking soda helps draw any moisture out once they're dry.
Either a roof rack or a trailer hitch cargo carrier would be useful for keeping them out of the 4 Runner.
