We have a one Rapid Groom vac and the big blue one, which can be set on blower and both do a really nice job drying even heavy haired horses. The bigger vac has two engines, so gets more force going for faster drying. The Rapid groom is light, easy to pack up for shows, gets used on horses, sheep, dogs at various times. Price was good at $10 used!
I killed two people hair dryers and only got one shoulder dry before going to the horse vac. Shop vacs work fine too, put the hose end on exhaust.
A tip with vacs, is to have a skinny nozzle on the end of the hose. This forces air coming out into narrow space, creating friction and HEAT in air coming out nozzle end which speeds things up even more. I cover damp horse with cooler, flip up the corner on area to dry, work my way around the horse to dry it. Then take the damp cooler and hang it up for next time needed.
You CAN dry a horse with layering on coolers only, just takes time. Water will come to the top of the layers beading up there. I use 2-3 coolers depending on how heavily haired the horses are. Probably will take at least an hour, maybe more to get fully dry. I remove the outer cooler layer as it gets wet. Under layers will then bead water on the top cooler until you remove it. Most of mine take 2 coolers to dry, but 3 is not unususal since ours are not clipped. I do make sure they are dry before going back out or stalled and left. They get very little work in winter, mostly outside at a walk for short times. So fairly easy to dry off.
The zebra clipping idea is unique! I am going to try it come spring and they are working harder. Also will share with my friend who clips hers because they are in work and blanketed. Very interesting, so Thanks for sharing!