For a scale effect, paint the plug with the undercolor and let dry. Take your scale mesh and stretch around the plug. You can hold the mesh in place with binder clips, clothes pins, or something similar. Hit the plug with the top color. When doing the scales, a light shot with the paint is best. Too much and it cloggs up the mesh and smudges. Remove the mesh and paint a line down the back of the plug to fade in. Takes a little practice, but once you get it, it can be fun.
Nice selection of plugs too
Jigman