A clipper that is designed or small for whisker or ear trimming, may not work on his mane; all depends on the clipper.
I use an Andis Cordless clipper for bridlepaths, and fetlock trimming, as well as whiskers\ears. I use a 15 blade for bridle path, and 10 on the fetlock area and ears. I use a 40 for whiskers. If I am lazy, I will just use the 15 on the whiskers too...lol!
"The ideal horseman has the courage of a lion, the patience of a saint, and the hands of a woman..."