I'm having trouble getting a good finish with my topcoat.

The first question I would ask is why are you topcoating? ALL-IN-ONE Paint has an exterior grade sealer built right in that is more durable than what you're adding to the top of it. Anytime you brush on a clear coat, you run the risk of streaking, cloudiness (especially on dark colors) or yellowing (especially on light colors). It is important to smooth the topcoat out, leaving a wet edge. Do thin, even coats and apply more as necessary. If you've applied a topcoat and have these issues, you're best bet is to repaint and leave the paint as is.