Have you looked on the EasyCare site? THey have barefoot trimmers and farriers listed (kinda like a classifieds section, so it doesn't mean they are endorsed by EasyCare). Or try here: The Horse's Hoof, News for Barefoot Hoofcare
on the side bar they have a trimmers list, but some are more Strasser type trims (and are more invasive and likely to cause soreness) That is probably why the $150/horse trimmer is allegedly making them sore, seems there are more Strasser trained trimmers in the North/Eastern parts of the country. You would probably want a Ramey type trim or Jamie Jackson, they are not invasive.
$150? Dang, I need to move up there! I charge $30 and get odd looks sometimes!