Mammoth Uncensored Word List:
22 words ending with f, 12 letters long

antidandruff burglarproof counterbluff counterproof doityourself draughtproof feedingstuff handkerchief nonfireproof outfangthief poultryproof quarterstaff remorseproof scratchproof shatterproof stretchproof treasonproof troubleproof undersheriff weatherproof whisperproof wrinkleproof