Airbrush or spray can?
If you're airbrushing or using a spray can and getting a rough, lumpy looking finish, then you have an effect known as "orange peel" (the paint finish looks like the skin of an orange).
This could be caused by:
- insufficient thinning of the paint (thin the paint some more)
- temperature being too high or very low humidity, causing the paint to dry before it has time to level itself (don't paint when it's too hot)
- paint applied too thickly, (and sometimes combined with high temperature/low humidity) causing the paint to skin over and surface-dry, while the lower layers dry at a slower rate causing shrinkage and unevenness (this can also cause cracking/crazing or a snake-skin like effect) (apply multiple light coats rather than a single heavy coat)
Often, while you can take steps to minimise orage peel, it may happen regardless. You may need to wet sand and poilsh to eliminate it. Applying more paint won't level it.
If you are using a spray can and are getting a honeycomb-like effect with tiny bubbles embedded in the paint,
- you are applying too heavy a layer of paint and have dissolved propellant out-gassing from the paint on the surface of the model. This may happen if you are moving the can too slowly across the surface or spraying from too close a distance. Spray several lighter coats from a greater distance rather than a single heavy coat.