Why do tiny white spots appear on my finished acrylics?

The white spots and bubbles you are seeing are most likely one in the same. If a bubble is suspended in the enhancement and you file part way into it, that bubble will become packed with dust, looking like a white spot. Working overly wet or dry with your mix ration can cause bubbles to form, but your application method has a big role to play in bubble formation as well. If there is air trapped in your brush, it gets pushed out into your product as you work. Ensure your brush is thoroughly and evenly saturated before you pick up your bead. Try not to pull a line through your powder as you may have a tendency to pull air into your bead. Instead, try to just dip your brush in the powder. Ensure your mix ratio is right. The wetter you mix, the more shrinkage and the more bubbles. On the other hand, the drier the mix, the less monomer can saturate the polymer, resulting in large voids where there is no liquid, also creating a bubble. — Samuel Sweet