I'm slow too.
My process:
- Hook up black tank flush hose and turn on (that spinner thing).
- empty black tank
- close black tank, fill it again through the black tank.
- empty black tank while monitoring clear elbow
- If I still see toilet paper or anything, I repeat again (or if going into storage for month) otherwise done.
- then I empty the grey tanks
- add some water into the black tank, put digest packet into toilet/tank
- add some water to grey tanks, put some deodorizer down sinks
This was based on a video I watched.
If the hose I use to fill the black tank back up is slow, I'm slow. I'm guessing I'm 20 minutes to get this done on a good day.