Here's a good article about kalk.
http://reefkeeping.com/issues/2005-01/rhf/index.htm#3
I have a large system, about 500 gallons of actual water volume. I was kalk with my ATO. I have one container of RO/DI water and one of kalk mixed with water.
I use a duel head dosing pump , and dial in the evaporation rate.I can adjust the amount of RO/DI or kalk water volume going in to match my evaporation or kalk demand. More kalk. dial down RO/DI, less dial it up. Same for kalk.I use 2 65 gallon water storage containers, and feed to the dosing pumps. It drips into my sump near my skimmer intake.If you use a dosing pump, and only drip in small amounts, it's hard to over dose.If you use a float valve , etc for ATO it could be a lot more of an issue.
How big is your tank and alk demand? A small system might be able to get away with a pretty simple design , even using a drip system designed for two part. Most times you can keep up with alk with kalk dosing only. I only came close to not meeting my demand when my tank was very full of sps and things were growing like crazy. It could go through around 5 gallons a day of kalk water to match evaporation and keep alk stable.
What ever method you chose, have some way to dose it very slowly, so it is harder to overdose. HTH's.