Another useful tip I spotted on Facebook this morning, haven’t tried it myself yet but I think its worth a shot. If you have tried it please let us know if it worked for you.
While cleaning the bathroom, fill the tub up with a couple of inches of the hottest water you can draw from the tap. Heating up the bathroom 10 degrees above the normal air temperature “doubles the effectiveness” of alkaline cleansers. It’s a trick housekeeping and hotel staffers use.