I don't know the best way, but I can tell you the way I that I do it (that works for me).
And a ziped .psd showing the layers--->
http://premium1.uploadit.org/JeSTeRs...ter-engine.zip
I use the base layer as a mask in photoshop.
Draw it using the polygon lasso tool.
Next I use the magic wand tool to select the outer area of the new shape, then reverse my selection (this gives a better edge I think if you use the wand at anti-alias on and set the tolerance at about 20-25%).
Next I pick a brush size of around 17 with fade (set flow to around 10%) and airbrush the very outer edge top and bottom (not front or back).
Then I pick a brush about size 65 and block a bit more shade in.
Same for highlight. . .
Let me know if this helps?
