Just got back from 13 nights at the POFQ. This is the magic band I used:

I posted before I left but thought I would give an update/
I used acrylic paints. They are much easier to paint with than nail polish, even using a narrow brush. I then covered it in two coats of a clear acrylic sealer (purchased at Michael's and sold near the acrylic paints for a couple of dollars). I got tons of attention and complements and questions about it from other guests and CMs alike. Some thought I bought it that way. It held up perfectly for the entire two weeks- no cracking, chipping, or rubbing off. I never did go swimming but it got plenty wet from rain and water rides. So it hasn't been tested for prolonged time in the water. It was also scratch resistant.
As you can see, I also did my nails to match. I found the same color pink as my MB in Sinful Colors (Pink Forever). I then painted on top with acrylic paints and then used a nail polish top coat. I have to say the Sinful Colors nail polish held up very well. I never touched up with more topcoat every day like I often do and they lasted about a week at the parks before they started to chip. If I had bothered to touch them up, they probably would have lasted longer.
I thought I would see other decorated MBs out there, but I never saw any. Just those with the little sliders or characters you can buy.
Anyway after my trial, my suggestion is: save the nail polish for nails and use acrylic and sealer on the band. It's cheaper, and you can get many different colors and shades. For your nails (if you like to match

) try Sinful colors.