Deakon, I'm with you on the "paint-it-all-first" technique. I've tried it a bunch of ways, but in my opinion, that's the most efficient way. If you do any amount of weathering at all, the trax and running gear all become one grubby color anyway, so even if you have rubber wheels, just slop some black or dark gray on 'em as best you can, and cover up the slop with your weathering later.
Check out my E-100; that was all painted after the build, even with the skirts on.
Well, I did kinda pre-shade by blasting everything under the skirts with flat black before I glued them on, but all color was applied afterwards.
The E was real easy, since there's no rubber. I even freehanded the track color on with the AB, just trying to avoid getting overspray on the wheels. Washing and weathering tied it all together.
Deakon, your Tiger's looking FANTASTIC!
You know, if it was me, I'd leave it gray...