How to remove soap scum from a bathtub

I was faced with a terrible soap scum build up on a tub and shower when a tenant moved out two weeks ago. I thought OMG, how can I even show this apartment until I find a way to clean that tub and shower!! Somehow I came across an article on using Easy Off "fume free" oven cleaner (in the blue can). I was skeptical, but decided to give it a try. Sprayed the walls first, then the tub - I used the entire can. Smells like lemon - no chemical smell. I waited about 90 minutes because it was so bad. When I went back to it, it didn't look any different so I took the shower head down and turned on the water and started to spray the walls. I couldn't believe my eyes . . . the nasty scum was sliding off the walls! I did have to use a sponge that has a nylon scrubber side in a few spots but for the most part the oven cleaner took care of it all! I am still in shock that it was so easy. I will never scrub another tub/shower again. Thank you Easy Off !