Depends on how big the wrinkles are. If you can srape the wrinkle without cutting into the cloth and get it adequately smooth...that's what I'd do. Then go on to fill. If the wrinkles are too big I'd cut/sand/scrape the wrinkles out. Patch with 4 oz. cloth, or 6...if that's all you have. Scrape and feather the patch and then go to fill coats.