I've started version 1 of a brush for zbrush made specifically for the hard surface dynamesh process. Each primitive can add or subtract from the main shape and step up in resolution nicely to be polished. I made the shape above in only a couple of minutes using this brush.
So far it's pretty basic shapes. I'll be adding more to the brush and re-posting new versions.
Try it out - Download HERE
More on this process can be found below: