Hello there.
Cool looking bike, the way you have it set up so far. Painting cranks and rings isn't the best way to go, really, as they suffer so much abrasion and abuse even during regular use. These pieces are generally anodized when new, as such a surface finish is much more durable than would be either paint or powder-coat.
But - who knows - it might work out for you; give em a try, and see how it all works out ...