I would think the flakes need to "float" in the epoxy, yet sink enough to make it smooth.It would be like a pearl paintjob on your car, the pearl will float out, then clear coat after. You would need to make sure the epoxy is compatible with the paint you're going over, and bind properly, not react. That's the nice thing with real epoxy, it's thick, where paint is a thinner finish. I know I will never use anything other than real epoxy again, since the last shop was acrylic "epoxy"(****)1 step paint. It was thin and wore off in a year wherever the tires rolled, or any traffic was involved.
Experimenting is fun, but if it screws up, it's 25 times the work removing the mess!