Here's another cheap drip method:
Get a cheap (but new) clear 1 gal. jug
Drill a hole in the top (barely large enough for rigid air line, 1/4" stuff I think)
Insert the air line into the top (should be snug so it won't rest on the bottom)
Slip air tubing (cheap clear 1/4" silicone or plastic tubing) onto the top of the rigid air line
Attached needle valve (again just the cheap air flow valves)
Draw a siphon and let drip (like what Biggles was talking about)
This is best for Alk supplements (for stability) and Kalk (has to be introduced slowly, due to the high pH at supersaturation). It only requires that the jug sit higher that your sump's water level. You can raise and lower the rigid air line to adjust your daily dose. This also can help eliminate the risk of dosing too much. I used this on my 30g breeder:
And my 65g (this was my upgrade from my 30g):
WARNING: Always dip. AEFW's caused me to tear this tank down. I miss it.