King Louie, it's very simple. I'm sure you can do it.
Suppose you want a red sparkle. Strip the shell, remove glue etc. Sand. Apply a thin layer of primer (terpentine based, I'll explain why later). Apply a thin layer of red laquer. All of this with a brush, no need for expensive spray paint. After drying, sand lightly. Then cover the shell in a reasonably thich layer of colourless laquer. Sprinkle red glitter flakes on the wet laquer. until completely covered. In fact you should overdo it a bit. the surplus of flakes will fall off and can be re-used. tap on it lightly with a clean hand (this way you push the flakes in the laquer). Allow to dry for a day. rub slighty with hand, to remove non-stuck particles. Apply a thick layer of colorless laquer. When this layer is dry but not yet hard: take a clean piece of baking-paper, put in onthe surface en rub strongly to smoothe the surface somewhat (baking paper won't stick). Allow to dry. DONT SAND!!! because you'll sand through the firts layer of laquer easily and you'll sand the red of some flakes, making them silver!!! you don't want that. Aplly a couple of layers, day after day, sand in between very lightly. After a couple of layers it all kind of smoothens out. The more layers the smoother, depending on tast. Use only high gloss paint. When it is mooth enough, sand strongly with 120, layter 180, 240. Then apply one last layer of spraypaint (on terpentine basis, not thinner basis like car paint, it will ruin everything!!!!).
Terpentine based paint flows better than water based paint.
I advice you to make tests firts to get the hang of it.
Good luck.
