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There are probably some helpful tips and/or hints in there somewhere, but there is also a lot of gumpf.
As a quick and easy solution, here is a pic of one of my finished marines:
The method is thus:
Paint (almost) everything that isn't black first. I tend to do it in this order: Base, metalics, white/stone.
Then clean up all and any mistakes you may have made with plain ol' black (I use Vallejo Model Colour black, as it is a little more 'matte' than the GW Chaos Black).
Then, splosh some black onto a pallette and mix in a teeny tiny bit of Codex Grey. I mean, teeny. The paint should be almost indistinguishable from black. Apply this to the top 2/3rds of every armour section, leaving a fine line of pure black right at the top. Then mix in more grey, and repeat, leaving a little of the previous layer showing at the bottom.
Rinse and repeat until you have about 50/50 black/grey.
Finally, mix up a little more paint at about 1/3 grey/black, so significantly lighter than the previous highlighting, but much darker than pure Codex Grey.
Use this mix to add a final 'edge' highlight to any particulaly sharp edges, or areas that need a little definition.
It might sound long-winded, but I think the results are worth it.
-t.