Bubbles, spots or a ‘fish-eye’ appearance in the finish is caused by excessive air and foam, which is why we recommend stirring and not shaking colors, and why we prefer cellulose sponges to foam brushes.
This can also be caused by dabbing the color on too thickly and overworking an area with the sponge. Sometimes the bubbles will pop before the finish dries, but if not you have to disperse them more without introducing more air.
To correct this, try polishing and thinning out the dried bubbles with a sponge dampened with water. If this is ineffective, try a rag with alcohol. Take care with alcohol, as it may thin out or melt any repair made with filler.
Once the surface is even, dry, and no longer tacky, apply a thin coat of color (or more if necessary). Let each coat completely dry. Always stir the color; don’t shake it.