Save yourself some money!
Go down to Smart & Final (or any place that has janitorial supplies) and get a quart bottle of their generic liquid toilet bowl cleaner. It shouldn't cost more that $4.00. It is an acid based cleanser that will absolutely, positively remove any organic scum from your bottom, even if it has dried out. Squirt some on a wet, long handled brush, or make a mixture in a bucket. (try to keep it off your hands) A little goes a long way. Wipe it on and hose it off. That's all it takes.