Aww, poor boy :(
I do use eZall. It won't completely remove really tough stains, say grass stains on white hocks (
), but it does help and it makes the job easier when you go in to scrub with some elbow grease. It has worked on just about every other stain I've used it on, though.
You attach the sprayer to the end of your horse, spray the solution on the horse (it comes out all sudsy!), and wait a minute. When all of the bubbles have gone away, you rinse the horse off. For ordinary maintenance bathing, it's a godsend! I even use it to bathe my dog. xD
When preparing for a show, I usually bathe with eZall once, then bring out the big guns and scrub down with another shampoo (usually a color enhancing shampoo), rinse, then run the eZall cycle again. And just a note, I have a paint - so you can really
tell when a shampoo works or doesn't! Lol =)
I think it would be safe for your sensitive boy, too. All of their products are biobased (even the truck and trailer wash!). They have a quick spot remover too, like the Cowboy Magic product, but I have never used it. =)