"I usually get metallic paints painted on smoothly, but parts of Celeborn's armour (Battle Of Mirkwood series on Mithril) are tricky, even when following all the rules I am aware of: the metallic paint layer came out a bit gritty in spots. The primer layer was smooth, so this was not the problem.
Before I paint the metal colour parts of a model I first shake the pot of metallic paint well for at least 20 seconds, ensure a reasonable consistency (no tackiness or wateriness), then shake again before using.
Then I ensure there are no obvious specks of grit in the paint by spreading it out thinly on a palette to test it.
Then I draw the brush backwards along the palette while twisting the brush to get a reasonably thin layer of paint on the brush the whole way round until the layer of paint on the palette is dead flat but not sparse.
Then I barely skim the surface of the model, using the tip of the brush only, as best I can. To avoid grittiness and unevenness, at least on the tricky areas, I find it necessary to take my time and barely cover the model, flattening down any accidental unevenness.
I find it easier to skim the model at a slight angle, holding the brush slightly towards the model in the direction I am painting, rather than skimming at a right angle.
I paint in straight lines in the same direction in each section, with a slight overlap between strokes.
I paint long cylindrical armour plates from end to end to avoid a build-up of paint on the other side of the limb. I paint these plates in the less awkward direction.
I don't restroke sticky paint until dry so as not to get a rough coating, though I find a little restroking of a stroke of paint immediately is ok if I have missed a significant area or if I have accidentally applied a little too much paint from pressing down the brush a bit much.
I have greatly improved my metal paint finish on my tricky models, such as this Celeborn, using these principles to the best of my ability, though some spots on him were still a bit gritty to a lesser extent than before. Lightly skimming these areas with paint greatly flattened them; and a careful even rub of a rubber helped where the grit was more isolated.
Both techniques seemed adequate because I had already done a reasonable job. It seems that there is a tendency to press the brush a little too hard on the awkward areas and apply a little more paint than can be applied on smoothly, despite trying hard. I suppose it helps when painting large areas of Rohir helmets to paint from side to side and away from the side of the helmet at the end of each stroke to get a smooth finish. " by G. Doran.
