Hi Brandon,
This is my opinion, but I am going to caution you against this. Foam flexes, chrome/gloss spray paint does not, which means that just one accidental squish, bump, drop, etc. of the helmet could result in creased and/or cracked paint that will be all-the-more-noticeable because of the high shine finish.
An alternative that you could do is to use Angelus Brand leather paints. They are made to bend and flex which makes them perfect for foam costumes/props, they go on streak-less with a make-up sponge, 2-3 light coats should give you full coverage, and the light coats dry within 5 minutes so you can get all of it done in an afternoon. Plus, they have finishers that you can apply to bring out a shine (you want their "high gloss acrylic finisher"). It will not be the same high shine/chrome look that you are looking for, but it will not be nearly as fragile as chrome paint on a flexible surface.
I hope that helps!
