I think what you have is this:
and although its easy to install, its supposed to be moistened which a lot of people don't do and can't have too much mud applied on top which a lot of people do.
Your problem is going to be at the end of the metal...the corner is going to look all kinked because its supposed to be one piece, or if it can't be one piece, joined together while dry to mold into each other.
My fear is you are doing this to solve one problem, and then create a new one...a corner that kind of looks like ass.
I'd go with the compound you bought. If I have setting type handy, I'll go with it, but just using that stuff isn't the end of the world.