Fwiw I dose from a 10 gallon static reservoir (basically just a 10 gallon aquarium with a lid). My process:
* Wait untill it's getting low
* Dump 60g of Kalk in (using 6g per gallon, but it's actually a higher ratio because I don't completely empty the water)
* Dump water in from high, so it mixes up
I've been doing this for over 6 months. I've never cleared out the old Kalk. I never rigorously measure. I never mix otherwise.
I've had tons of success with that setup. My gut is that if you have a doser that can repeatedly dose overnight, if you have room for a reservoir that can last over a week, it's very easy to do the static route.
I looked into the avast and mixers generally, and it seemed like a lot of money and work relative to the static setup, so I gave up on the idea. No complaints.