Snapped some pictures last night of my setup. As you can see, it's pretty ghetto.
So: Two timers. I have them set to turn on 8 times per day for 2 minutes.
Schedule - Alkalinity
00:00-00:02
03:00-03:02
06:00-06:02
09:00-09:02
12:00-12:02
15:00-15:02
18:00-18:02
21:00-21:02
Schedule - Calcium
01:30-01:32
04:30-04:32
07:30-07:32
10:30-10:32
13:30-13:32
16:30-16:32
19:30-19:32
22:30-22:32
The reason for the plug splitters is that each timer controls two pumps, since I dose into two tanks, it's easier to control the driprate individually if they're on their own pump. For the cost of an Aqualifter (around $10-20 depending on where you shop) this is an easy way to scale upwards. If I really wanted, ie., if the Aqualifter pumps fail, I could just as easily switch these out for say the "Drew's Dosers" at BRS and just adjust the on/off times to longer or shorter if need be. Or I could just get a Profilux doser (I do admit I like them, I just can't afford one right now).
The pumps and jugs:
I never throw anything out so I had lots of these ARM and carbon containers lying around. They are nicely about 1 gallon each and easy to open up and clean and refill. I drilled two holes in each, have rigid airline tubing through those holes so the pumps pick up from the bottom of the container, and then just standard 1/4" tubing the pump intakes and 1/4" tubing that go to their respective tanks.
The irrigation dripvalves:
Pretty ghetto, I just have the tubes dangling over the sump right over the return pumps intake. I test Ca and Alk weekly and adjust the driprates as needed if there is drift in any of the parameters. You can get away with using a single timer if need be, and thus add the Ca and Alk at the same time, but then don't do what you see here (ie., being added to the same location) - put the drippers in different spots so that the additives don't react to each other.