Howdy.
I've done the Iron Man. I'm not expert, but I can tell you were I had the most trouble.
Paint.
Iron Man is all about the right paint job.
I painted the whole figure in gold metallic, then used a clear red over that for a metallic red. This looked well enough but you'll have a devil of a time masking off the bits to remain gold. I used liquid mask.
My trouble area was sealing it up. The high gloss lacquer I used dissolved the acrylic red which melted down into the gold. Had to strip it and start again.
So, caution on mixing you acrylics and enamels, but it's a fun build.