You are right. You just need a more gradual transition of colour. Its about 1 drop of brown to 1/4 of a drop of white (maybe less). Thining it down also helps because it lets the lower level of the colour shine through better. Keep in mind this is still the "easy way" of blending.
For the real way to blend check out Ali McVey's videos here (note she uses 2 brushes, 1 for each colour she is working with, and pretty much everything that has been said about colour and paint thickness still applies).