I've found this a couple of months ago, neither the Land Speeder nor the following instruction is from me, it's from a forum which I can't remember anymore. Whoever you are, I love your Black Templars and I thank you for the painting instructions! =)
Engines with the glowing effect:
Paint them white inside, mix very watery blue tone (Enchanted Blue here, if I remember correctly) and then let the watery paint flow into the deeper areas. A hairdryer can help reducing the time for drying massively.
My Ork bommer with the applied technique:
The hairdryer is really needed, as it takes ages to dry by itself.