You make use of scent elimination clothing like Scentlok or Scent Blocker. Although it might be expensive, it is actually a good investment. It best that you start out with buying scent eliminating boots, since people's feet usually give off scent which strong for animal sensibilities.
HHO is the best fuel. HHO is green fuel for our own blue planet. HHO is 2 hydrogen and 1 oxygen molecule and nothing else, so it burns clean and actually breaks down existing carbon deposits left by propane. HHO is highly combustible. We recommend use from the "bubbler" amongst the HHO 1000Kw Diesel Generator and the connection to the intake against your own engine.
When using your grayscale gray tanks while dry-camping, it's fine to leave your gray tank open, but don't dump your black tank until it's over half full. Use a commercial-grade tank additive, actually a homemade answer. The same chemical should provide in both tanks.