Go for it...
I admit...using Macerator toilets fills the black tank pretty quickly. It would be nice to...
Open Black,
When SeeLevelII BlueTooth app shows 0%, Open Flush water valve,
After a bit of time to flush black tank...close black.
When Bluetooth app shows 4% on black, turn off the flush valve. (Precharge)
Then open gray valve...
When app shows 0%, close gray valve.
All while having coffee inside, out of the rain.