You've got a lot of good answer here.
However, I want to clarify something - Mod Podge and PVA glue are not exactly the same thing.
From comments I've seen on my tutorials and based on STEALTH foam armor tutorials - these 2 products don't behave in the same way. If you go with PVA glue, you'll have to thin it with water (to a milk-like consistency) and apply a lot of coats (STEALTH suggests 5 in his tutorial). As for Mod Podge, I would avoid it completely - it is not flexible enough when dry to make a durable finish for foam armor (that's my opinion).
I've been using a different product for years and only had good result with it - but it's a bit more expensive (and harder to find) ... and it will give your similar result of using PVA glue (but I need to appley less coat). The product I'm referring to is Flexbond from the company Rosco.
Lately I've been ordering from these guys:
http://www.stagestore.ca/product_info.php/products_id/707
Regardless of the product you'll be using - the process is the same.
As Grave mentionned already - you need to seel the foam first (PVA), then paint, then use a top coat.
If you want an even more durable paintjob, then you can seal over the paint again and then apply the top coat as the last step.
Finally - as for your last post question... I don't think you can acheive the same result. The armor pictures looks like a resin cast and if it is, then it has very different properties than your foam armor. The foam you've used seems to have a very strong texture... so even after all the sealing and painting - this will still show through and might not look good in a silver/chrome only setup.
Best advise we could give you - is try it out on foam scraps first.
Then you'll see exactly what your suit will look like after the whole process and you can decide to continue with the silver or go with red and gold.
Good Luck!!!