I'm surely not an expert on kalk, but i do use it through my ATO. It definitely isn't the best technique, but it is easy for me and it works. A doser or kalk stirrer is probably better. I have to deal with changes in evaporation, but I've gotten good at adjusting my kalk mix over time. My alk swings more than I'd like it to, but it's an acceptable range. Typically between 120 and 140 ppm.
That said, my acros are getting big enough that kalk is struggling to keep up. I've recently started dosing a little alk and cal manually to keep things steady. I'll be in the market for a cal reactor soon.