Spread a dropcloth out on the floor or on a clean surface outside. Set the ladder up underneath the ceiling tiles you're going to remove first. Climb up the ladder.
Lift up on the first tile you want to remove, according to Painter Click. Turn it on its edge until you can slide it out of the suspended grid. Continue this step with the remaining tiles.
Spread the cardboard ceiling tiles out on the dropcloth with their exposed sides (the sides you see when they're hung in the grid) facing up.
Pour some wall paint into a pan. Dip and roll the paint roller into the pan; begin painting the cardboard ceiling tiles. Apply even coats to each tile, according to Painter Click. Don't paint the edges, just the exposed sides. Allow the paint to dry thoroughly before you reinstall the tiles into the ceiling grid, following the recommended drying time on the paint can.