Get a copy of Dick's 2nd edition book and look for the tables.
The easiest way is to get some pipettes and pipette pumps. Its quite easy to mix any mixture from 4x5 up to 20x24 print sizes for those doing real negatives (and extremely easy for calibrated Pictorico negatives).
Dick calibrates his digital negatives with a 2s or 3s mix. Unpublished work also resulted in a 0.5s mixture.
One trick for a long printing session is to make up a larger batch of 2s mix, then just measure out enough for a single print. Keeps at least 6-8 hours without a noticable change in contrast.
and if you must use drops, for NA2 10%, 5%, 2 1/2% mixes - get some B&S brown dropper bottles and droppers (plastic droppers, don't use glass...too variable in drop size). They're the same ones that B&S sells in the kits with 25ml.