I reshaped a bowl brush to fit through the bowl valve hole. Since I added the hand wand with separate valves for the wand and the flusher, I use the hand wand sprayer, reshaped brush, and toilet cleaner to clean the area I can see.
While this won't clean the plastic above the valve, it won't "look" dirty when the curious want to watch the "action" when flushing.
Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW