I have a horse that is body clipped and lives outside, but it doesn't get quite as cold here. She does wear a blanket and neck cover. Your clip will go much easier, use less blades, and look better on a clean horse, but it will take a while for him to dry with long hair, so be prepared. Mine didn't have a super heavy coat and we have radiant heaters in our wash rack and it still took forever. Use tons of Show Sheen, too. Makes the clip easier and look better.