I put them in plastic bag, sprinkler some supplement in (type depends on day in dusting schedule), and then shake 'em up. It's just like getting the butter in microwave popcorn bags to disperse!
I don't tend to dust my pinheads.
They already have a 2 to 1 calcium to phosphorous ratio.
I would only dust them when you are supplementing with D3 or a multivitamin.