The biggest waste of money on that set. You'll beingnspending more money on canned air than anything else. 

I would never use glass droppers. Buy plastic droppers instead. Cheaper. Even better if you can find them in bulk. I've still have a small batch of plastic droppers to last me a few years. If I need more, I know the source to get more.

I rarely use droppers for paint. Mostly for thinner. I eyeball by counting how many drops of thinner to my paint. 99% of the time, I'm spot on on the paint : thinner ratio for airbrushing.