I use the Cowboy Magic concentrated detangler and shine (not the shampoo or conditioner). I have never had a matt it didn't dissolve. They have a website with a store locator (usually farm and horse supply).
www.cowboymagic.com
You can also purchase it at
www.tobysnaturalpets.com and also check out the life for teeth spray while you're there - it works instantly (and lasts) for bad breath and removes tarter.