Drywall – How long does setting-type joint compound have to dry before priming

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.

You can use either all the way through. I have personally used both all the way through more than a few times and have mixed. There are generally some differences.

• the lightweight end mix is thicker, meaning that the regular can actually be better for a final coat since it goes on thinner
• the lightweight is easier to sand but I hardly sand... so this hardly ever helps me
• I personally think the lightweight dries out faster
• lightweight does scratch and dent easier due to less density

Pros will use the regular since they can use a "less fluffy" mix that feathers easier (with little to no sanding). But I could definitely see why a person with less experience would do the first two coats with regular and last two with lightweight.

Answers to your questions -

1. You are both a little right/wrong. If I had to choose I would pick him.

2. If he knows what he is doing he doesn't sand much and doesn't need lightweight.

3. I answered these above. The marketing for the lightweight is for the novice DIYer that hates to spend hours sanding...