Need Advice and Questions answered. (Painting Gba)

[arena slicer]

So im planning on painting my Gameboy Advance. (and my Sp probably)
Ive heard people say that you should take sandpaper to your case and scuff it up real good. (if someone could explain the concept of this to me)
Ive also hear that a clear coat is recommended for repainting a portable device because the paint gets worn of easily. (wondering how long it takes to wear off)
Also i will be painting my gba with krylon fusion spraypaint. (most recommended as far as i can tell)
If someone could please clear some of this stuff up for me.
Thanks in advance

 

[grossaffe]

supposedly sandpaper makes the paint stick better by creating a rough surface, however Ish says he doesn't bother with sanding, and Montana Gold is his preferred paint of choice.

 

[watsug]

If you do use montana gold, make sure to buy clearcoat/varnish. I didn't on my N64p and the paint can be peeled with just a fingernail.