Chris - I swear you're a lifesaver, gentleman and scholar when it comes to this stuff!
Yes, oily steel is definitely a bit sparkly, but it's a little known fact that the Wright Cyclone ran on glitter. I'm actually planning exactly what you suggest, hitting it with smoke and then a black (well, more of grimy, almost-black grey/brown) wash to grunge it up.
Good to know about the wateriness. I wandered off to my LHS during lunch today for more paint-buying fun and they actually had a bottle of Liquitex airbrush medium. Think I may try both your suggested mixes and see which I like best.
Regarding the colors...I actually discovered something very random that makes me question whether or not some of Vallejo's colors are labeled with the wrong FS numbers.
Sprue Brothers, Great Model, and Vallejo's own PDFs all identify non-specular blue grey FS35819 with Model Color #904, Dark Blue Grey. Clearly, from the pic I posted above, it's not.
At my LHS, they have a Vallejo equivalency chart zip-tied to the rack, and on a whim I decided to look it over. Sure enough, FS35819 matches up to Model Color #904, in rack position 157. BUT it lists the paint name as Gris Azul Claro (guess they only printed the spanish chart?), when Dark Blue Grey is Gris Azul Oscuro. I've never seen this anywhere else, as all the other materials just stick to the stock numbers.
Gris Azul Claro - or Bluegrey Pale, as the call it, is #905, with an FS of 35237. Looking at the chips online, it appears VERY close to 35819. Maybe a touch more on the grey side.
Can't help but wandering if there was some labeling error...but I picked up Bluegrey Pale as well as the confusingly named Pale Greyblue, with some Sky Blue if I need to blue either of these up a bit. More paint testing tonight!