Matt is a beast when it comes to texturing, and that is a really nice model Thumper.
I usually use GIMP, with varying opacities and brushes (like the galaxy brushes etc), use green, purple and blue to add speckly layers to a grey background. (for steel)
I then darken and lighten areas that seem appropriate, e.g any edges that I feel need highlighting get a thin light streak.
Basically many layers of varying opacity until I like the look of whatever I'm doing. (I'm not too arty so it takes quite a few layers
)
