I also definitely recommend using Thetford green. Use the entire recommended amount and add a "Potty Toddy" tablet. You can buy those at Camping World - they also have an online store. When it is hot, you may need to add more Potty Toddy tabs if you have an odor issue. Do not forget to put the lid down after each use and flush a long time (maybe count to 10), not just briefly. Leave the lid down unless using.
When we first started out, we used a pre-packaged chemical powder that absolutely did not work.
I was really grossed out and didn't even want to use the commode until I found that the Thetford/PottyToddy chemical mix really works.