sorry for the slight lack of pictures. I don't have a legit camera, so I took most of them on my computer's webcam and one of them with my cell phone.
Step 1: Ingredients
Step 2: Add citric acid and soap to the tank
also, try to mix as you put it in. the citric acid should be dissolved as much as possible. same with the soap.
why not use vinegar, you say? well, for two reasons. first, vinegar is very voluminous. it would take too much space. second, it is smelly. you would be given away when the bathroom smells like nasty.
Step 3: Put baking soda in the bowl
I would say this should also be about a cup of baking soda.