One of these days I'll tell you how brussels sprouts got their name... 
Dishing is okay for more forgiving metals or shallower domes, but for something like this helmet dome, you want to "raise" the metal. Like so. I have a batting helmet the exact right size that I can use to make a hydrostone negative form to check the fit. Planishing is just small-scale shaping to refine and smooth the surface.
[ETA: Found it. Try this. This guy does great tutorials.]
I may have to talk to you about circuit-board-y stuff. >_> My further plans involve much pushing of electrons...
Also, shoot me a PM or e-mail when you want to get started refining your templates.
--Jonah