i ran a body shop from 1972 to 1975. acrylic laquer, acrylic enamel and "regular" enamel paint were the primary products in use back then. at the end of my body shop days, the "new" imron epoxy paints were starting to become popular but these were still essentially single stage applications.
the appearance of single stage metalic paint is determined by: the mixture ratio; the air pressure at the gun; the distance the gun was from the painted surface when the paint was applied; and the spray pattern set up on the nozzel of the gun - i.d. larger fan to smaller "spot" pattern. when one paints a large pannel, all of these factors are consistent, or at least should be. these factors also are the reason why single stage metallic paints need to be applied in the same initial application on the entire car. if you do not watch to ensure you are applying this paint consistently, you will get the "tiger strip" pattern/problem where you can see darker stripes in the paint. generally the cure for tiger stripes is to apply another wet coat of paint at a further distance from the painted surface.
all of the noted factors are also the reason why it is harder to "spot in" older metallic paints to get a consistent color and look. the only way the new "spot in" repair will look closer to the older original paint is if the repair spraying conditions are as close as possible to what the spray conditions werre for the original non-repaired paint.
generally, the "pattern" of the metallic can also be affected by altering the paint gun spray pressure. you can experiment on a piece of metal using this variation. finally, more metallic can be added to a single stage application by thinning the paint down to where you are spraying more metallic particles than paint color. this application applied with the proper drying temp thinner in a "wet" manner across the entire painted item will result in a much heavier appearance and consistency of metallic particles.
as to repair and your problem, you might try a fine grade rubbing compound first on a not so obvious area of the car to see if the paint on your car can take any abrasive element before the color and/or appearence is noticably affected. also, make sure you avoid rubbing compound heavily on angles and creases of your body panels. the paint will rub off of those areas very quickly as the paint is not very thick at those points.
as a final suggestion, if you want to try to wet sand your paint, start with very fine paper - like 2500 and HAND sand an area with large circular motions with very light pressure and lots of water. if you wet sand old metallic paint with heavy pressure in a small area with back and forth strokes, you will see a color/appearance change almost immediately.
hope some of this helps...
