Carbona Washing Machine Cleaner worked really well for me. I had soap residue along the sides and bottom of the washer. My dark colored clothes would get this soap scum on them. Washing them again would just do it again. I tried other additives but none of them worked.
I had read other reviews about Carbona Washing Machine Cleaner. They were very positive, so I gave it a whirl. Carbona Washing Machine Cleaner worked so much better than the others I tried. After using this, the bottom of the washer was shiny and like new. Only trace amounts soap build up was left. Carbona Washing Machine Cleaner worked a thousand times better compared to what I used before.
Walmart had great deal on it as well, so purchased 4 more bottles.
Here is a tip: The directions on the Carbona Washing Machine Cleaner says to run the washer on normal cycle with hot water to clean it. I have an HE Samsung washer, that it has a cleaning cycle. The cleaning cycle worked great!