Paint thinned down Mephiston Red to the coils, the edge around them and the vents at the front.
Using Evil Sunz Scarlet carefully paint the edges of the coils higher up. Do the same with the vents slightly higher up to begin a gradient. Paint around the edge of the coils with a thinner line too.
Using Wild Rider Red repeat the above step, taking it a little higher again.
Using Fire Dragon Bright repeat the above step, taking it a little higher again. This time when painting the coils focus more on the edges either side of the gun and less in the middle.
Using White Scar create very small highlights on the corners of some of the vents and along the very edge corner of the coils.
Finished product with the rest of the highlights and details.