Walls and Ceilings - Gap between new walls and old ceiling

I put in new drywall in my bathroom and there is a gap at the top. At it's widest the gap is slightly less that 3/4". It seems like I can use j/c to fill it in, but it also seem like the compound will need something to grab onto. I posted in the paint forum (I also had a paint question), but this question seems more appropriate here. Is the gap too big for paper? I read the problems people have with mesh tape, so I'm nervous about using that to fill in the gap. Would using a setting type compound instead of general purpose help with the cracking?

Thanks for any help. Jimbo

You can use quick setting compound to fill in the gap. Make it flush with the face of the drywall. Mix the material rather thick. After it dries tape and spackle as normal.

Thanks for the advice. That worked great. I used 90 minute compound, because the short working time with the other stuff made me nervous.

The next step is to skim coat the whole wall. It's a bathroom wall and we're going to use a satin paint, so I want to make sure we have a nice smooth surface and no "shadowing." I've read that using watered down lightweight j/c is the way to go. I bought lightweight setting compound for the gap, but there is also premixed (the only kind they had at HD) lightweight general purpose j/c. Are either of these options fine?

Also, the ceiling (plaster) is in rough shape because of some mildew problems. I want to skim coat that as well, before repriming and painting it. It seem like the roller option is the best way to go there, or should I use thicker (regular strength) j/c and skim coat it that way?

Thanks for any advice.

Either one should be fine. Lightweight material is a liitle soft after drying but it will work. As far as the ceiling goes, make sure to clean it very well and kill any mold present. I would use the 90 mix for filling any deep holes then skim with the lightweight.