Learn how to apply a skim coating of drywall compound to a wall.
Thin joint compound so it's loose enough to apply with a paint roller but not so thin that it's runny. Put a metal paint roller screen into your 5-gallon bucket and you won't have to transfer the material to a tray. Roll a uniform coat onto a wall area of about 40 square feet.
Use a 12- to 14-inch drywall knife to immediately strike down the surface. Leave a thin uniform coat with a minimum of tool marks. Deposit the removed material into your drywall tray, then dispose of it. Dumping it back into the bucket could contaminate the batch with dried bits and other impurities from the wall.