Re: Paint prep
Me, I'd use a 220 grit on a DA, and follow it up with 400 grit by hand, sticking to horizontal strokes. But, I have more sensitivity to surface defects.
Hint: a DA or palm sander will leave curly-q's or swirls. They will be visible from every angle. hand sanding with a lighter grade horizontally will minimize the viewing angle of sanding scratches.
Pick a panel to test on, paying close attention to your paint/reducer ratio. When you it the magic ratio for the temps and humidity, one that allows the paint to flow out without runs...