Skunk repellent at the den...and hopefully the den isn't in the horse stalls! See if you can find it... predator urine or another repellent specially made works...

but the cheapest and quickest, if you don't have other animals that walk about the same area... hot pepper powder! Sprinkle it about and they get it on their paws and lick...

as for if it's sprayed places... spray those places down with a tomato based solution (including clothes and skin)... tomato juice etc works great to remove the smell=== at least it used to in MO... maybe their constitution had changed there?