Technique with any spraying is important, but I'm guessing you're already figuring that out! My guess with the frames it that you had a lot of overlap in areas where change of direction was necessary. Too much material in one spot which runs and sags. Much easier to see what's happening on big open surfaces. On narrow things like frames, you can reduce your fan width which concentrates your spray pattern but in turn you need either dial down material flow or move faster. Getting gun further back with narrow fan will be your friend on interior surfaces. It's all about anticipating the "how will I do this" prior to pulling the trigger on your newfound toy.
Usually, the longer you can make your sweeps at constant speed the better. Smoothness counts. Nice thing about sand-able primer is do-overs are pretty easy. Try and imagine the best way you can accomplish an even coat without excessive material in corners and overlaps. Ideally, getting enough material on but staying just shy of runs and sags will give best results (wet coats). "Dry" coats will leave texture and look uneven. You'll have better feel when you get to topcoats.
