As said above, a fluid bed is a necessity for any self respecting jig crafter.
My recipe: Take a plastic jar, drill a hole in it and glue in an aquarium pump tube. Now take another identical jar, cut out the bottom and glue in laboratory grade filter paper(coffee filter doesn`t do the trick) instead. Now plug the filter paper jar into the first jar - done ready.
If you buy a double-outlet aquarium pump, you can combine for instance whit base and second coat clear with sparkle pigment etc. for extra nice pearlescent effects.
The beauty of this system is that you can make many inexpensive paper bottom jars to store your paint in - one for every ground color you use. No need for messy re-fillings, and you can still use the jars for brush-tapping.