Sometimes the best way to thin a mane (not straighten it) is to use a very dull shearing comb (with the long teeth on the sides snapped off). Let the horses mane get dirty and a bit messy then reach underneath the mane and pull the comb firmly in a downwards direction, it will grab the hair and thin it out without you having to actually pull and straighten the mane. It's good for people who want thinning but not straightening......oh your lucky to have a mane that needs thinning! My guy has dental floss for a tail and mane right now