Uh, that depends... I usually paint the basecoat and a first highlight, apply the wash and then add two more extra highlights.
You can also just paint one layer of paint and add the wash, the results of which you can see here
Or you can add the wash after the stages shown by Tom.
I'd say that the time depends on the look you want to achieve. If you apply the wash last, everything gets a nice shade and the wash ties the different colours together and also give them a "dirty" streets-of-Mordheim look. If you add extra highlights after the wash, you have the nice effects of shading, but the colours will be brighter.
(now, correct me if I'm wrong, I'm not a master painter unfortunately