Hi pa340dart,
I don't remember plum crazy as a metallic back in 1970 but, perhaps someone else who has worked with that color will chime in.
If it is a true metallic you would want to use a base/clear coat system. If you get some trash in the base color coat you can sand it out and reapply some base color. Then you apply several coats of clear. If you have trash in it you can cut and buff and not disturb the metallic flakes below.
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