Drywall question - How do I get crisp edges at the top and bottom of a wall?

Hello, I'm doing some work on my apartment. I have removed the "popcorn" ceiling which had been applied to the concrete slab. I'm in the process of putting WeldCrete on the ceiling and then applying joint compound as a skimcoat in order to produce a smooth surface.
On the floor, I'm pulling up the parquet tiles and having a cork floor installed. I have removed all of the molding from the base of the walls and I don't want any moldings after the cork is installed. The cork installer said he would run the cork under the wall and I could use joint compound to fill in the bottom of the wall to meet the cork. I would tape off the cork at the bottom of the walls and remove it after applying the joint compound.
Do people have any suggestions on how to get a nice crisp line at the bottom of the wall? Should I try to use some kind of metal corner piece down there? Should I apply something behind the bottom of the wall so the joint compound won't all fall into he space in the middle of the wall? Also, I was wondering what to do with the top of the wall. I don't want to put joint compound in between the wall and the concrete slab because the wall will move and crack it. Should I use a metal corner piece up there?
Any help would be appreciated.
Regards,
Larry
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You can get edging for this very purpose. At your Home Depot, Lowes, etc. you should be able to find trim shaped like an "L" or "J" with paper tape on one leg that can be mudded to your drywall. The stuff will be located along with your standard drywall corner beads, etc.
I most often use this stuff on the top edge of drywall where a suspended/hung tiled ceiling essentially "sits" on the wall (spanning two rooms, for example). With your floor, depending on how level/flat it is, you may want to ensure you have a bit of extra room (~5/8" from the floor, or whatever allowance you need for the bead plus space for your parquet tiles.
B

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Ben, Thanks for the tip. I'm going to put the bead on the bottom after the floor has been installed. There may be quite a gap at the bottom of the wall because the new floor is thinner than the old floor. How do I fill in the gap? I think I want the bottom edge of the wall flush with the new cork floor. With this "L" tape you mentioned, I guess one leg would just stick under the wall and would not need to be mudded, right?
Regards,
Larry

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