My mixing methods:
First, I transfer all liquids which I purchased in large quantities (such as nicotine, PG and VG) into more manageable 50ML bottles with drip caps.
Next, when making small taste batches of say 5ML, I am able to drip the drops from the 50ml bottles with ease. And because I am using mostly MBV flavorings, as well as their 50ml bottles, the drippers from both the flavoring bottles and the nic, PG and VG bottles are nearly identical in volume, making my drips consistent throughout.
When I make large quantities, I again use the nic, PG and VG from the 50ml bottles, but instead of painstaking count 100's of drops from each bottle, I remove the dripper and use 1ml "oral syringes" (no needles at all and they fit perfectly through the neck of the MBV bottles) and insert the syringe into the 50ml bottle and draw up what I need 1ml at a time and transfer to my mixing bottle. I also have separate syringes for each nic, PG, VG and each ingredient (if it is more than say 1ml to be added to the batch), thus preventing cross-contamination. I also use a sharpie and label each syringe (above where it will enter into the ingredient) then put a piece of scotch tape over the label. This way I don't get them mixed up and can use them multiple times in one sitting when making more than one batch of juice. After I am done mixing I thoroughly was them with water and let them dry out for re-use next time (with labels still intact).
You can get the oral syringes from your local pharmacy, and if you are a regular there, they may do like they do with me, and give you a handful of them for FREE. If not, the cost of each syringe will probably be less than 25-cents each.