I suspect that most of the big batchers measure their OOs by weight, but this could be difficult to do in small batches, particularly if your scale measures only to tenth ounces (rather than hundredths, or grams in tenths). In that case you probably need to measure by volume.
Depending on the amounts the dropper might work for you. I've heard from chemistry people that drops are often very uniform so if you use just one dropper you should get pretty good proportions. However, can you see yourself counting out 700 drops?
I found these
borosilicate graduated cylinders at Edmund Scientific, and they would perfect for measuring intermediate amounts. They come in sizes of 10, 25 and 50 mL and cost about $10 each. The 10 mL is about 2 teaspoons (1/3 fl. oz.), the 25 mL is almost 2 tablespoons (0.8 fl. oz.), the 50 mL is 3 tablespoons plus 1 teaspoon (1.7 fl. oz.). The 10 mL is calibrated in 0.2 mL steps and the other two in 1 mL steps.
You could either measure EO then pour into a mixing container, then measure the next EO, or you could just continue on in the same cylinder by filling up to the first amount, then switching to the next EO and filling up to the combined amount, etc. Use a dropper when you get almost to the desired amount so that you won't over fill it.
I think I'll get one for myself, except that I'm lucky enough to have a lab glassware supplier only a couple miles from my house, so I can just do a drive-by.
