The heat stress looks excellent, could you describe the process you used
I painted shaded highlighted the gun. Then with an airbrush, I lightly sprayed a very watered down army painter weapon bronze round the end of the barrels then a very watered down Vallejo imperial blue(blue/purple) followed by a watery Kantor blue then some matt black at the end. Make sure you leave a little of each colour showing.
This could also be done with a brush, but would have to water the paint a lot and wait for it to dry between the layers would take a long time.