Something just doesn't sound right. If what you describe is true, there really is no solution. A shelf well above the bottom of the main tank will always collect solids.
You can get wands that you hook to a garden hose and shove it down the toilet but to keep up with it, you are going to need to do it every 2nd or 3rd dump.
Odor is a different question that is unlikely to be related:
- Check that the roof vent is clear
- Check that the toilet seals are fully closing.
- Check that the seal between the toilet and floor is in good condition and in the proper location.
