Before you initially dump the black tank, try and add as much water as you can. The closer to being full, the better. That way you'll flush out as much of the solids as possible. Dumping the black tank is the 1st thing I do when packing up to leave.
Then hook up the in-tank flusher and let it run for a while you break camp. I let it run for as long as 10 minutes then go peer down the toilet to see if the tank bottom is clean. If not, I'll add water to the tank and repeat the dump then flush process once more.
It really helps to add 3-5 gallons of water in the tank before each use as it can prevent solids from sticking to the tank bottom. And don't scrimp on water each time you flush. Trying to conserve water can cause a lot of grief and extra work and if bad enough, the flusher won't help you.
If you have to use a dump station, often you can't hook up to their hose bib plus if you have other RV-ers behind you, you don't want to hold them up. As noted above, use another color of hose for the flusher (not white for potable water) so that there is no chance of contamination of the potable water supply.