Just remove the wheels and wash. If you don't want to remove the pads why not just hit them with some sandpaper after your done? If your worried about "crap" absorbing on the pads you should get a bike friendly wash. I never remove my pads on my CX bike and never have had an issue. I use the pink wash stuff and water. If I feel performance dropping a bit and pads are still plenty thick I will hit with the sandpaper and I am good to go again.
I know its apples to oranges but you don't do anything to your cars pads ever.....