[SactoJim]

I imagine most satin type paint jobs are single stage instead of 2 stage (base/clear). There are satin type clears out there and/or additives you mix in with a regular clear to dull it down.

I'm not real familiar with some of these satin finishes, but single stage paints have gotten better over the years in regards to UV protection which is what can "break" paint down and cause it to "chalk" up.

In regards to buying it online.....there's some good deals to be had, but if you are buying a particular color, buy extra in case you have a "do over" or you need some touch up later. This will insure that you have a good color match.

I don't see any reason why you can't later apply a glossy clearcoat over your existing satin finish as long as it's prepped correctly.......ultimately I'd check with the paint manufacturer.