HOW TO COAT CORNER BEAD
Professional Coating Techniques
For the 1st coat you will need a 10 inch knife. When you're ready for the 2nd coat, do the same exact thing but use a 12 inch knife. Always keep your pointer finger in the center of the knife, this will give you more control. Always try to keep the finger side of the knife as dry and clean as possible. Most knives have a logo or something on 1 side. I always make the logo side my finger side. Decide what side you want your finger side to be and stick to it. If you're flipping the knife all the time it will get all wet, dirty and sloppy and gross. You want your pointer finger to stay dry.
STEP 1: Mix mud, Spread
Mix up your joint compound (With water) until it is thin enough to work with. For more on mud and how to mix go here
Using a drywall pan and a 10" knife, spread a nice even bed of mud on one side of the corner bead. Try to go from the ceiling down a little past half way.
STEP 2: Feather In Outside edge
Place your finger a little to the right of center. As you pull the knife down the corner, apply a lot of pressure on the outside edge (See Picture) See the ripple line , that's what you want. Once you have feathered in the outside edge, Put your finger back in the center of the knife and wipe down the bead again, this time using firm even pressure on the middle of the knife.
STEP 3: Clean Edge
After you coat one side you will get some goobers on the outside edge of the bead. The picture below shows the other side of the corner bead we just coated. Take your knife and just glide it up the corner to clean the edge off. If you leave the goobers there, it will make things more difficult when you coat the other side of the bead.
STEP 4: Repeat The Same Procedure on Other Side
Spread on mud (A little past half way down)
Feather in outside edge, pull down the center
Clean off edge, Now you should have the top of 1 stick of corner bead coated.
STEP 5: Coat Bottom Side
It's pretty much the same thing all over again. Spread it on, Feather in the outside edges, Then pull the knife up the center using firm even pressure, Clean off the edge. Where the bottom meets the top you will get 1 little ripple line (See Picture). This is called a lap mark or fish tail. Before you 2nd coat, you will have to scrape that off or sand it. If you get good at coating bead, this will be about all the sanding your corners will need.
That Is How To 1st Coat Corner Bead. Lightly sand and repeat procedure using a 12" knife for your 2nd coat.
Here is a free video to help