2) Now I use a blue wash in the recesses. It's all about surface tension, you want a really watered down mix. I typically use the GW Asurmen blue and water it down even more, I don't know what the new color is called sry.
That's pretty much it, you just keep working on the color till you're happy with it. I originally started working on a metal Vanguard Vet but released the inside of the thrusters were very rough. It made the process much harder, you might want to clear the inside of the thrusters with a Semi/Gloss to increase the surface tension and allow the paint to run off the edges and sink into the recesses.
I hope this helps and makes sense ..
Here are a few of the pics from the Vanguard Vet ... I had to paint it more than let it run into the cracks itself.