I usually pressure wash and then caulk or patch any visible gaps. Then prime with a good exterior primer. Then paint. For my business, we use Dunn Edwards Paints, specifically Permasheen/Evershield or AcriFlat, depending on the look you want to create.
As far as the painting itself, we use Graco airless sprayers to lay down an even coat. Be sure to use a paper masker along the roofline and lay the paper onto the roof to prevent overspray. Removing screens can help if you are inexperienced at masking, this way if your masking lifts during your spraying at least you can scrape the windows. Use blue tape, don't cut corners, and take your time. Don't spray a second coat until the first coat is dry, and spraying less is better when you first start to prevent runs. Usually you can rent a sprayer for not too much, or even buy a basic airless for around 300 bucks. Plan on power washing and caulking one day, then let everything dry overnight. Then start painting the next day to be sure the substrate is dry.