that's an interesting technique....I went to a local outdoor animal park & took some close up photos of Macaws, plus a worker gave me a couple feathers to use as references.
What I've ended up doing is spraying a base Stratto HoK blue down on the tank. Then I cut some general feather shapes out of card stock paper and used it has a free hand shield. Lightly spraying some lighter metallic blue next. I glued some plastic bristols off a cheap house brush onto the edge of card stock paper and sprayed a darker blue over the feather shapes to get a feather like texture...I lightly spray it here and there to give the over all appearance of feathers across the gas tanks....looking cool so far & not sure if I can post up a link here to show off my final work??