The coating resin is naturally thicker than laminating resins, so air entrapment that can cause low spots in the cured finish is always likely to be an issue, unfortunately
Allowing the resin to stand for a little while before applying can help, though, as craters can be left by air bubbles popping at the surface without levelling again. Try not to over brush during application as well, as this will only cause more air to become mixed-in that might not have time to escape before the resin starts to gel.
If you're working in cooler temperatures (below 20 degrees C), warming the resin a little and keeping the part in a warm-ish place will help
Another source of imperfections can be little nibs of dust that settle on the part during cure, so it might also be a good idea to place something like a plastic storage box over the part once it's been coated.