Now, this is just a theory, as I haven\'t tried it, but I think it might work decently, especially if you\'re doing a lot of models.
Prime white, or even better, grey. If you prime white, then go over all the areas that are supposed to be black with a medium grey or grey-blue. Add a touch of black to this and thin down into a glaze. Glaze over the whole area that will be black. Make another glaze, a bit thinner, of pure black and glaze again.
I\'ve found that the \"multiple wash/glaze\" technique is actually pretty decent, especially for \"speed painting.\"
(A great example of NMM bronze done with the multiple wash technique can be found in the bone thread by EArkham.)