[Phlogiston]

That really depends on what radio you are talking about. Sometimes it is ok to "mask" (or use other process) to darken the accents/base/whatever and then spray a toner over the top of it all - say VD brown on the accents then topped with med brown walnut - just don't use too much of the walnut and the dark areas will stay dark (rather than brown).

In some cases an airbrush can give a better effect than masking.