Usually when doing collision work and repairing a dented fender for example I will usually have no or very little metal actually showing. I'll cover the bare metal, then have the result like you described Toro, but I don't like putting it over sanded paint. Feathered out into the existing finish yes but never over sanded paint. Just the way I have done it. If you were to do it I'd only do it over OEM paint sanded with 80 and never over refinish paint.
Keep in mind that for the highest quality it's always epoxy first then filler, but lots of times that isn't possible, due to the type of job and how much you are getting paid to do it. You've gotta factor that in JC.