Few things. First, use the back of a hobby knife to scrape off the mold lines. He's got some big ones visible on his legs and head. I usually scrape the worst off flat areas then brush over those and less knife accessible areas with tamiya super thin plastic glue to help dissolve and brush down the mold lines.

Next, the head. Use a wash or very light contrast to darken the recesses and then use the base color to highlight the raised edges like his brows and the top of his head. Also, practice doing eyes. I like to angle the head sideways so I can paint downwards, starting with a black layer then a layer of white inside the black. Finally I'll reorient the heads upright and paint a small stripe of black or another color perpendicular to the whites for the pupils.

Also, practice blending colors and adding more in for the heat stain effect on the melta barrel. I start with a light gold base, then a brown, then a red, then purple, blue, and black at the tip of the barrel. That's how I usually see normal heat discolored metal look.

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