Steve, I know you have been here before. I have tried this method of dusting the sparkles on wet paint. It looks great but it is a monster to get the paint thick enough so sanding doesn't become a sparkle spoiler.
The best method I have found so far and it still is goopy but seems to retain the sparkle best is mixing the sparkles into clear. And then spraying the mixture directly on the guitar. I also use a base coat of black as it seems to make the sparkles really well, sparkle.
But this is no easy task painting a sparkle caster folks. Steve is probably the leading expert around these parts. I am still debating what to do with my silver Stratocaster I painted last year. It looks great but it is bumpy in some areas. I am thinking about taking it to my friends body shop for a glossy coat and polish. Or just living with the bumps??