The guy at Home Depot didn't know what Krylon Exterior Spray Paint was? Good Lord, now I've heard everything!
Go to Michael's
. That's where I found it, and the acrylic craft paints, brushes, rhinestones, and beads. And glossy polyurethane should be fine. Whatever your preference.
As for which hat, it kind of depends on what you want to do. I don't have a facebook account, so I can't see the pictures you've posted. But if you're painting the whole thing, then the stiffer hat will probably be better. If it's got a shine to it, you might want to knock down the shine with some really fine sandpaper or steelwool first, then wipe it with a damp paper towel to get the dust off, and let it dry thoroughly before painting.
If you're just going to decorate, then either should be fine.
As for a picture of my first hat, here it was in it's most pristine state, right after I finished it. (But now it's even more special to me, as it's slowly being covered in autographs)
I'm sure you've already seen Andy's. Pretty much painted like the team helmets, dark blue background with the logos on either side, and "Texans" painted on the front in the "official" font.
Let me know if you have any other questions!