Your post could mean one of two things. If you are talking about an every day mix - say for a highlight color then:
ya . . I use old brushes or sometimes the heel of my own brush to mix up stuff. I rarely get caught up in percentages - it\'s all done by guessing, eyeballing, whatever.
My only problem with the eye dropper thing is:
1) I don\'t need anything more I have to clean. I usually paint for several hours at a time and use up to 50 different colors in a session. If I had to clean a dropper between each one I\'d go nuts - even cleaning once is too much. And
2) a drop is not always a drop. A drop of thin paint is not the equivelent of a drop of a thick one. And how do you measure the difference? Apply some viscosity test? To get it chmically equivelent is a huge waste of time as paint even in the bottle is inconsistent to it\'s neghbors and also changes over time. GW usually requires some water every time. Some Vallejo\'s do as well - some don\'t. And the next time I sit down some seem identical - some are worse.
Typically I take one brush of stuff - put it on the pallette wipe it clean - get a drop of the other color, apply it to the palette and finally a drop of water. As I add highlights I wipe the brush (not with water) and add more of the lighter color and mix that in . . .
Part II
But if you are mixing up a whole bottle of new paint then:
I defer to the others - I think I would try pouring anyway - adding water to make it pourable or of it\'s thick as GW can be then using a brush to guide it. Sounds messy.
Actually I am tired of mixing up a really dark gray but I think I will buy the Vallejo Game color Black and and some white and just squeeze them into a new bottle until I get the right shade . . .