Now that you have the dings spacled, you might consider a light skim coat over the entire wall surface w/ light sand or topping joint compound. When dry, lightly sand or sponge any ridges down and using the light, touch up any areas for a smooth surface. One good coat of primer followed by two finish coats color.

I agree with sierraeast. I've repaired many large areas like this. You are right---that a shiny paint over this area will show the defect.

The best tool I ever used to do a big area like this is a 48" aluminum yard stick. They are about 3" wide and don't flex. Toss the mud on the area, and scree it with the yardstick. It gets everything level for you without so much fooling around.

I have never done anything that large before...never even over drywall tape...I may need to get someone to do it or risk a huge dust storm and lumpy wall! Thanks....the weird thing is that it feeld perfectly flat.

A friend just took a look and suggested I spackle over the affected area and lightly sand...just to give a bit of texture...he feels it is perfectly smooth already. Do you think this could work? Can I spackle over primer then re-prime?

Let me see if I can explain this a bit better for you.

Do you see a "ridge" where the original tape is? This is what I had invisioned in your first explaination.

If that is the case, you don't want any more mud over that ridge. What's going on is that not enough mud was put in on either side of the tape to get a good taper. That may be due to the fact that when the drywall was installed, it's not the meeting of the 2 tapered factory edges. It may be 2 cut edges. Which requires feathering of the mud way far out from the cut edge.

So begin the mud right under that ridge. Slap it on a smooth it out some. Then scree it. That will make it perfectly flat. After it dries, you can sand and fill in the little bubbleholes,etc. Good luck. This ain't hard to do at all. And yes---you can continue to refill even after you've primered the wall.

Thanks for posting this question.
I'm removing popcorn from the ceiling and have the same problem with taping.

Using the yardstick is brilliant! Before I get one, I'll try a circular saw guide. May not have a sharp enough edge, but it's worth a try? Any tricks to getting enough drywall compound overhead?
Thanks.

I think that worked...it looks much better anyway. Yes I think I was seeing a tape edge.

The way to do it overhead is to have the mud thick enough that it doesn't fall off the ceiling. Apply with a 6" compound blade, leaving it higher than the surface. You should pat it down a little so it's not so liable to fall off all over the place. Then scree it with the yardstick. It's gonna be a bit messy, but it's worth it because it cuts down on the time you're holding your arms up, working overhead.

Circular saw guide works good too, but be careful about using a good straight edge like this over and over for this technique because it can mess up the edge over time.