Drywall – Is it too late to add drywall tape

I know this isn't the answer you want to hear, but I don't think priming and painting will hide the tape.

Before you apply any more primer, I'd add another thicker coat of mud. Slather on the mud thick first - it doesn't have to be smooth. Then smooth it out by angling your 12" knife so it's almost parallel with the drywall as you drag it along the surface. You'll have to press fairly firmly in order to avoid air gaps appearing in the thick coat you're smoothing out.

You may have to get a feel for it. If you push too hard and can see the tape again, redo that section until you get it just right.

Wait for the thicker coat to dry, then sand the edges as smooth as you can get them. Very carefully/lightly sand over area covering the tape if you didn't get it quite smooth. You may need to do a second coat along both sides of the thicker coat to make it join the drywall surface smoothly.

There are huge differences. I am sure a professional tradesman can go over the exact specifics but here is my common man take (even though I have drywalled too many houses to remember):

• plaster generally sets more quickly
• plaster is thicker
• plaster can be applied more thickly (joint compound you get about 1/8")
• plaster to me is like working with thinset except you will see the plaster as thinset is almost always hidden
• joint compound can be sanded more easily
• joint compound is more prone to cracking (this is about application too)
• I would personally only use plaster for a very small area that is having cracking problems. I have done some plaster work and literally drove me nuts. Also I do not consider myself artistic. When applying plaster it is an art. If you over apply sanding it down is way harder than joint compound. I would never think about plastering all of a drywall in a house.

The only thing else I can add is I don't know what they consider slow plaster. I am sure that refers to the setting time. The plaster I have used starts setting in 30-60 minutes (hence my reference to thinset). Maybe they have something that lasts longer or maybe it is some combo plaster/compound.