Drywall Finishing Video
Going from a taped seam to a perfectly smooth wall is not that hard. You have to have the right tools A 10 inch broad knife with rounded edges is a must. Be sure the edged are rounded so they don't dig into the drywall. Apply a heavy second coat of drywall joint compound over the seams. The edges of the drywall mud should be thinner than the center. Leave a hump in the middle of the compound.
When the joint compound is dry, take a sanding pole and knock down that high spot in the middle. Then apply a third thin coat of joint compound. When dry, sand it down and you will have a smooth joint.
Follow these steps for a professional looking finish on your drywall projects.