I find that by starting with a 1000 ml Erlenmyer Flask full of the mead I'm going to tweak, I can pour off 100 ml increments and make additions to each of those using lower ml pipettes or other smaller measure devices and get the taste to where I want it.
Then I back-calculate and reduce by a small factor again, and make the addition to the mead. I let it stand for a few days, then go back and taste, if necessary I'll goose it once or twice with whatever I feel it needs and go forward.
It's worked pretty well for me, and I use it when I infuse with other stuff too.