I use the geo method as well. What I also do: when getting ready to leave the CG and it's time to dump (regardless of levels in tanks,) I'll fill the tanks with water--open a water tap for gray and use a stick to open the pedal valve on the toilet. Fill, then dump. Then, I fill again with clean water, dump both again. Then put a little water and chemicals (and ice if desired) for the ride home, and you're ready for the next trip. It takes a little longer (all the filling and dumping,) but my tanks are clean and I've never had any odor doing it this way.
2015 XLR Hyperlite 30HFS5 (mods being performed regularly)
2009 Salem LA 292fkds (gone)
Nights- ('12)23 ('13)23 ('14)15 ('15)31 ('16)25
2014 Harley Davidson FLHX (XLR cargo)
2014 VW Jetta TDI (diesel sipper, camping support vehicle)
2011 Ram 2500 CC 4X4 CTD, B&W Companion (toy hauler hauler)