How should I prep for a color change over existing good paint?

Thanks guys. The instructions for the base said 3-4 coats, so I decided on 3 for the jambs and I'll probably do at least 4 for the exterior The clear said 2 coats, so that's what I did.

Should I have been more hesitant to lay the clear down? It was actually surprisingly easy.
No...you did a nice job from what I can see in the pic. Don't try to make it shine with the first coat of clear. Just get enough on to cover well. 2nd coat, increase your overlap to about 75% and slow down just a teeny bit. Be careful on edges and curves and always work towards your wet edge of the paint. I don't stop on the gap of a panel, like between the door and fender. I start at the bottom and work my way up and go 6 or 8 inches over onto the adjacent panel. When I started doing that, I stopped getting little runs on gaps. You don't really have to cross back over the gap when you move to the next panel as long as you keep moving and don't let the wet edge dry out. You'll do fine, since the jambs look as good as they do.