Orange peel texture is applied over drywall that has been taped, mudded and sanded.
It is usually applied with a sprayer, which can be rented for about $45 a day, or purchased for anywhere from $30 to $350, depending on features and durability.
You will use a thin mixture of drywall texture to create the effect. You can purchase this ready mixed or as a powder.
If you mix the texture yourself, aim for the consistency of pancake batter. You may need to thin ready-mixed product as well.
To eliminate lumps, allow the mixture to stand, covered, overnight, then stir and strain through a screen in the morning.
This prevents clumping and powder lumps on the wall.
Use a moderate amount of pressure when applying the texture. If you are able, practice on a piece of cardboard or extra drywall to perfect the technique.
Keep the sprayer moving or you can end up with lumps.
If you don't like the results, scrape the wet texture off quickly and start again.