First of all you gotta realize... when I step in to a house for a bid, I act like I own the house. If I don't do that I have really bad anxiety... so I take charge right off.
When we are on the walk through and I see soap scum and a bar of soap I ask them this... do you know why bar soap does that? They usually say no. I say because it is made of lard... pig fat. Do you like rubbing pig fat all over your body? They usually answer... no. Then I say... that's why I don't use pig fat, I use soft soap... and move on. But it makes them think about it. Most of the time that alone doesn't make them switch... then after we clean a few times I tell them... you could have a clean shower for much longer if you would quit using that pig fat all over your body. 99% of the time it has worked within 3 times of bringing it up.