Re: paint sprayers
I spray ceilings- that's all primers, paints, and all ceilings. One small room I might roll, no more than that. It's the best way for ceilings. Doors, trim, and walls get sprayed based on the finish that's expected. Usually it's ceilings, closets, and if needed cabinets sprayed, then brush and roll the rest. Walls get a 18" roller, doors get rolled with a 9" then tipped, trim gets brushed.
If you aren't good with a sprayer, practice with it in your garage or on a shed. If after that you like the results go forward. For most latex, use a smallish tip like a 213 or lower- big tips put out as lot of paint fast and you need to be good to use them or you'll get build-up or runs. If you rent a sprayer to do a whole house, buy a new tip. Rental outfits don't replace these until they're totally shot. If you spray solvent-based paints, be sure the rig is grounded- check the plug and outlet both to be sure, or static can cause unwanted visits from the Fire Department.