I learned that trick from Model RailRoaders, so I can't take credit for it.
Just work drops at a time until you get the right mix that you are looking for.
Remember if it looks to dark, then wipe it off and see what color is underneath.
Don't be afraid to throw the sticks into 2 or 3 different mixtures.
Real wood has different shades all over it.
If you try it, show us the results please.