If I can add. I see a lot of people recommend the fiberglass mesh seam tape. For the life of me I canon understand why. As an avid DIYer I have done a LOT of drywall. Not like a pro bt I certainly have a few hundred sheets under my belt. I have used both paper and fiberglass and a few other variants. the plane old paper tape is by far the easiest to work with. You never see a pro use fiberglass tape. (At least I haven't). The paper tape helps you get a crisp inside corner, doesn't require as much mud, is more forgiving of aggressive sanding and is cheaper too!
I second the recommendation for metal corner bead.
I have never heard of dish soap. I just use a little water and mix. Ready mix, when not worked a little with a mixer, or in your working pan, is harder to use.