I was in the hospital a few years ago with my mom, she was on an IV and I just sat there watching it drip, drip, drip and thought hey! This would work great for my new saltwater aquarium as a way to top-off evaporated water! I politely asked a nurse about maybe, possibly, getting an IV bag to take home, new used, didn't matter. She said come with me. We went into the supply room and she just gave me a new one, told me "hide it, put it down your pants or something" LoL... I told her what i was gonna use it for and she said if the idea takes off and I patent it to let her know when she can pick up her share
Anyways, I used it for several months when starting out not wanting to buy an ATO, worked great! I had it set for a drop every 1.5 seconds on a 30 gallon tank, just about perfect... Then when I decided I enjoyed the hobby enough, bought an ATO and had this IV sitting around, then when I started adding stony corals and levels were dropping I utilized it for the same reasons you are, for CA and ALK. It worked OK but I would find coming back an hour later to check on it that it wouldn't be dripping anymore, it would often get clogged up with sediment. Not where you see the drip, but where you adjust the flow. I'd have to open it right up to clear the clog and then tune it back to a slow drip again... It wasn't long before I realized mechanical dosers are way more accurate than fiddling around with the IV.
It will work for what you're doing, but inevitably I think you'll realize that dosers are the way to go.
I think one of the reasons you're having success with this is because of the J-tube. It's not picking up the sediment like mine was when filling a bag instead. If it isn't clogging up on you then by all means, cheap and easy dosing method! If you're having to go to the trouble of mixing your new 6oz solutions everyday it might be easier for you do what George suggested and use measuring cups. Not sure what your daily consumption is but I wouldn't doubt that it's low enough that you could even pour it in one dose maybe 2 with no ill effects. Someone may be able to tell you what the max PPMs or DKH in a single dose would be