Applying Orange peel texture can be a very simple task. You can use thinned-down, Redi-Mixed wallboard joint compound. Make the consistency as thin as a pancake batter. Use a 3/8" nap roller to apply this mixture to the walls. A key point is that the coarser the roller sleeve is, the more pronounced will be the orange-peel texture. Make sure that the walls are completely dry before you paint on them. Also don't saturate the new textured medium or it could lift off and paint light.