Painting these helmets is a bit of a pain, because both helmets actually get more worn as the movie goes on, especially Ant-Man's. When he first puts on the suit, it's practically brand new and shiny, but by the end scene in the lab, the muzzle of the helmet in particular has become very tarnished and grimy.
If you are not on a strict time crunch, I recommend allowing yourself some experimentation time. Get some different rattle cans and/or airbrush lacquers, and then see if you can find an even piece of scrap wood, or even purchase one from a store that sells lumber (many have scrap sections where you can get smaller pieces of wood for less than a dollar a piece). Prime the wood with a few coats, then mask off sections and try some different combinations to see what you like best. I did something similar with my Civil War Ant-Man helmet (link in sig) and learned a lot about what different things look like when applied, how different clear coats react to with the base paint, etc. On pieces like this, that already have significant time and money invested in them, a little research will usually save you a lot of headache.
For what it's worth, I settled on Krylon Premium Metallic Silver followed by Krylon Crystal Clear and liked what I got. If you go that route though, I strongly recommend applying the Crystal Clear as soon as the paint's allotted 15-30 minute drying time of the has expired, no handling or washing or anything.