Not true. For one, black is very easy to attain and can be helped along with things like logwood.With brown and white, however, the difference in the metals involved influences very heavily the rate at which they accept color and the techniques used to create contrast. I've had barrels come out beautifully with relatively little effort, and others that it seemed no matter what I tried, striking contrast would not come. I'd like to say I've learned a good bit through experience because I haven't had severe issues lately, but almost every set of barrels is different. That in mind, I'm certain I'll still have occaisional problems down the road.
I do agree with Rookhawk, I've seen some of Kearcher's work that I thought I could do better on. However, since I didn't work on that particular set, I'll never know for sure.
This is why many won't fool with brown and white finishes anymore, and I wonder at times why I do.