I sprayed mine. I rented a sprayer. The sprayer was commercial duty, 4 tall legs, long hose.

Have they been painted before? Mine had been, so rolling wasn't so bad.

Messy job in any event.

We would recommend spraying for optimal results!

Sometimes rolling them can be a problem because the texture may actually just come off on your wet roller, usually when they have never been painted before. The sprayer is the way to go for this reason. I would use an airless sprayer with a 312 tip or so just because anything bigger and you can get into trouble if you don't know what you are doing. The paint should be flat.

Spraying.

Spray it with either a "ceiling white" or a dead flat paint in your desired color. Any sheen would only emphasize its texture. Most rental airless sprayers will come with a 515 tip. This will give a 10 inch spray pattern hitting the ceiling and be adequate for spraying a heavy bodied latex paint.

If the ceiling has not been painted in the past, be forewarned that it will suck up a lot of paint., probably about 150 to 200 feet per gallon. It will also take several hours to dry. Popcorn is nothing but chalk and reverts to mush until dry.

It was a common practice to not paint new popcorn, but to let it get dirty with age, and then paint it.

If it has not been painted before, then spraying is recommended.

If it has been painted before with success, then either spraying or brushing/rolling will be fine. Spraying has a finer finish, but rolling is better at getting everything white. The sprayer sometimes does not get every angle perfectly, as often there are jagged edges. Using a 3/4" or 1" roller nap (depending on popcorn length) works very well to get into the grooves. Provided the popcorn doesn't come off, then rolling actually gives a slightly better and more complete look.

Note: Brushing/rolling can be done if DIY, even if it hasn't been painted before, but be careful to make sure to test a closet or something inconspicuous first, to make sure the popcorn is not so delicate that it comes off with the brush/roller. Most of the time it wont, but sometimes it will.

Other notes are obvious- sprayer covers more ground faster, but with sprayer you must carefully cover and plastic every last thing in the house and all surfaces, cover vents and shut off return system, etc etc, to avoid overspray mist getting onto things it shouldn't.

If it is a smaller job, most companies/painters would roll, because a sprayer takes a lot of time to set up and clean hoses after job completion. This can substantially raise the cost of the project. If it is a larger job, most everyone who's qualified is going to roll- UNLESS the house is fully lived in and furnished.

When homes are lived in and furnished with a lot of furniture, clothes, dressers, items, objects, picture frames etc around the home, then you simply do not want to spray indoors at all.