I spend a lot of time trolling CMON (coolminiornot.com) checking out the paints, and using other peoples' paint jobs as inspiration for my own, as I have an extensive collection of miniatures without paint on 'em. Many of the painters on CMON are awesome; more awesome than I am. However, the more I view, the more that I'm not a fan of NMM (non-metal metallics).
My reasoning is this. I don't just paint for the sake of art, even though I do try my best and I'm always looking to improve. I paint for use in game, and I want my minis to look like they belong in a well-trodden world. To me, however, NMM makes the miniatures look just a bit too... tidy for adventuring.
Seriously, what self-respecting adventurer crawls dungeons with their armor looking like the bumper of a 1958 Chevy? How the hell can they do that? Dungeons are messy, dammit!
Thus, NMM is most likely one of the techniques that I will not try to utilize. I find that, for me, basecoating steel/silvery armors & metals in black with a drybrushing of Citadel's Mithril Silver gives the weapons & armor a look of worn usage that doesn't come across with NMM, while still allowing for depth in the paintjob. For brass, bronze, gold, and copper, I start with a basecoat of Citadel's Bestial Brown, and then while I do the drybrushing & detailing I paint over it with either Citadel Dwarf Bronze (for coppers & bronzes) or Shining Gold (for brass & gold), followed with a coat of Citadel Flesh Wash ink, which give the depth/shadows, and gives these two metallic types a worn and used patina.
That's what works for me. I totally respect the painters who use NMM and find their work well done, but it's obvious (to me at least) that these minis are not used on the table. And I realize that's a generalization and I'm sure there are exceptions, but I guess that's just how I see it.