I paint most of my cube mods and use 2 coats of paint then 2-3 coats of spray laquer. It hasn't peeled yet.
As for metallic paint, I wouldn't. I got a set of cubesmith metallic stickers and in most light it is difficult to tell apart the red / orange faces and the silver / gold faces. This makes for a severe penalty when speedcubing.
Please take off topic discussion off this forum. Thanks.