Especially for darker spots, or spots where there is just a lot of contaminant that'll get into the water and folex and try to run or just generaly be a pain to pull out with just a towel, I have a bigger spray bottle that I use with the nozzle nearly open to just soak the bejeezus out of the spot after the scrub. Then I use a shop-vac in wet pick-up mode to pull it all back out. For really stubborn stuff, sometimes a couple of passes with folex are required. After an outdoor outing at a kids park a few months ago where it had just rained, the bottoms of my feet were just solid black when I got done; I pulled almost all of that back out this way, even the stuff between the pawpads.