I tried cornstarch and was brushing it out of his coat for days after. The stuff is just too fine and Harley's coat is so thick. Might work on a summer coat, but it was a mess when I tried it on him. Too bad, that would have been a cheaper solution!I used to use dry cornstarch for grass stains. I never tried it on urine/manure stains.
If it doesn't work, cornstarch makes great gravy