For wood, I sometimes use a stock I put up of the now-defunct Testor's Wood Enamel, also over a wire-brush scratched surface (brass for plastic, steel for metal). I have painted tool heads so many different ways I cannot remember. I have tried Testor's "Steel" enamel and Vallejo "Steel," even Vallejo "Oily Steel"; also Tamiya and Testor's (enamel and acrylic) and Vallejo and AK Interactive "Gun Metal"---egad, what else? In every case, I have painted any tool clamps or attachments to the tank in the adjoining color as if the crew bothered to take the tools off before spraying camouflage. For US tanks, I have used the types of finish above, but also sprayed others all OD (which was often done right at the factory) or even a matte finish (imitating the lacquer sometime applied to the metal heads on US tools).
I don't think I have done tracks the same twice. Plastic tracks I leave alone. For metal tracks, I always used a Rustoleum primer (gray for US, red for DE, whatever for RU). Over the primer, I have tried the gun metal of the brands above, black, even--what a hoot--"steel." The last set me to
, for when all was dried, the tracks look the same as out of the box. 
I have always used a rust or track wash, sometimes as an enamel, sometimes as a powder pigment with a fixer.And then there are the nifty German Tetra fire extinguishers. I have used the reddish Vallejo puts out for shear handles, a reddish brown, even Dunkelgrau.
In short, I have tried many ways, following first this book, then that, then no book at all. So now you see why I asked, if you aren't
already.
