So what will you need?
Dawn (the original blue stuff)
The recipe is a 1:1 ratio, so equal parts of vinegar and Dawn. Here is the important part--you want the vinegar to be hot. I put it in a glass Pyrex measuring cup and microwaved it for two minutes. If you use smaller amounts, you might not need to heat it that long. I used a cup of each, in order to spray down the whole shower. Put the hot vinegar and Dawn in a spray bottle and flip it over a few times to mix it without shaking it too much.
Now spray it all over the shower (or the area of the shower that you want to clean). It won't run all that much, so you want to saturate the soap scum areas (otherwise when you wipe it down, you'll have clean areas where the gel was and soap scum surrounding it).
Okay, so I forgot to take out my hair and body stuff when I sprayed it down. Don't do that. It's annoying to clean up. This part of the shower didn't have a whole lot of soap scum on the walls, so they aren't saturated as much as, say, the area under the products where all of the soap and junk collects. Once you spray down the shower, leave it alone for two hours (or longer if you have really stubborn yuckiness). After that time, get a sponge wet in warm water and wipe everything down. Most of it was just gentle wiping and everything came off--there were a couple parts where I had to scrub. Regardless, it all came off! After wiping it down, spray it with your shower head (or if it doesn't reach, just get a bucket and dump water on it to finish rinsing it).
Voila! All clean! It's somewhat time consuming, but if you figure that the majority of the time was taken up with Isak napping and me watching SVU while doing laundry, it doesn't really matter, right? Now I need to find out if this works on shower liners. No amount of cleaning seems to work on the liner curtain!
Have fun and happy de-scumming!