Is it necessary to mask off walls when spraying ceilings and trim the same color but different finish? We’re using a Graco Magnum X7 spray gun to paint our 2100 sqf interior Sherwin Williams High Reflective White (painting over 12-year-old off white). After masking off everything that can’t be painted (eg. outlets, vents, vinyl shutters, etc.), our plan is to 1) Paint the ceilings with flat using a 515 tip; 2) Immediately after, paint the trim semi-gloss using a 315 tip. This really only includes door frames and doors, the latter of which were removed and will be painted in our garage. 3) Once our ceilings and trim dry, we will mask the trim and about two feet of ceiling along all walls. 4) Finally we will paint the walls (two coats) an eggshell using the 515 tip. Our assumption is that because it’s all the same white, we only need to mask the ceilings and trim to ensure they don’t get eggshell overspray. But should we also be masking the walls when painting ceilings and trim? I suppose the answer depends on if eggshell sprayed over flat and/or semi-gloss overspray looks any different in the end. Thanks!
There are as many opinions are there are painters out there, but in my experience, the order in which you paint surfaces changes when you move from roller to spray paint. When you roll, you do ceiling -> trim -> walls, but when you spray paint you do trim -> walls -> ceiling. The reason is that it's a lot easier to cover walls than it is to cover ceilings, and overspray can be a problem, even with experienced users. I use the 3M advanced masking film, because it comes folded, so that you only have to deal with a 1' wide piece to tape, then once the room is taped, you unfold it. I have not tried other brands, but I'm sure that they are good too.
As for the sheen, it really depends on the level of detail you expect from the work. But I would tape it and be on the safe side.
Your plan is fine and I have used similar methods to spray many of houses. Spray the ceiling, a 515 tip is fine. Spray the trim, personally I almost always use a 410 FFLP (fine finish - low pressure) - a 315 might give you issues as the fan is smaller with quite a bit of volume. You might have issues with the paint sagging if you don't move fast enough. If you had a 310 FFLP that would work great. After the trim has cured, mask it. As far as the ceiling, I typically just run 12" paper on the ceiling and wing the outside edge by folding it down about 2 inches and tape it. The wing will keep your overspray from traveling out past the paper by redirecting it and forcing it downward.
Some will say that it is advisable to scuff the overspray from the trim on the walls, especially if using a gloss and I have done it both ways but it depends on how much you spray up onto the walls. I try to keep my fan on the trim and just barely spray the walls.