As much as I hate buying chemicals, I'm an easy off Bam girl for the shower. It is the best thing I've found to get rid of the scum.
DH hates the shower head in our ensuite so will only use the main bathroom shower (I don't care - nice bathroom all to me ), but I am anal about rinsing all the suds/shampoo/conditioner etc off and away before I get out of the shower. My shower has much less than the main shower where DH wouldn't even think of that.