I keep my driving horses (Clydes) at Sargent Equestrian Center in Lodi. They have a very extensive training program and train from minis and ponies to drafts. They have all the equipment to use for a variety of horses (harness, vehicles, etc) so you don't have to make an investment immediately. This allows you to have the time to make sure you get what you really need and what works for your horse. I totally recommend the trainers there.