i tried ALOT ,
for regular maitnance , getting seascum , water line marks from mooring for a week or so ,
i apply the blue fsr , let it sit for a few minutes , watch it magically disappear , then rince with soapy water ,
for tougher rust type stains , Bar Keepers Friend , apply powder on wet sponge , dab on stained area , again ,
watch it disappear , rinse well , or use a seperate sponge to wipe up , wash with soap , apply some wax , Whala , like new in all my
cases , hull is always like new
( dont get Bar Keep on certain metals and let sit , it will corrode , would take time , just rinse within minutes and its fine !! )
FD