I run my mixes through a program. I take the cmyk of the color i want and this program gives me the ammounts of paints to be mixed.
My limitation is a drop (0,5 ml). If the program tells me for example:
To make 10ml of a particular color
6 ml of black
2 ml of blue
1.5 ml of white
1.5 ml of yellow
Im just makingup these colors but, the pippete gives the ml quantities, but when i get to the decimals, i use drops (google a drop to ml converter). If it breaks down to even smaller fractions, i increase the overal paint quantity to 20ml for example so that i get to that minimim base measurement of drops. Some times its a waste of paint because i wont even use 2% of the color i just made, but i store it anyways. Maybe one day it could be useful.
I sometimes use my "eyeometer" and round off the decimals cos then id just be a rivet counter. No judge will ever put a colorimeter on a model...
Hope this is understandable and it helps.
Cheers