My humble opinion…..
Ive never seen one of these touch up jobs that turned out decent. By the time you mess with it over and over, easier just to strip her down and repaint/decal the whole thing and be done with it. Or just leave it be if its just a motor that will be used.
You could try going really slowly over the decal with a decal remover pad, bring the paint back to life with polish, then install a new decal? That may turn out ok?
I cannot personally see any situation using new paint that would turn out decent, except for painting the whole thing of course.