craftgrrl | Trading Spaces/Slipcovers

I'm moving into my first apartment come September and will be taking a not-so-lovely sleep sofa with me. It's a simple shape- but too simple for a ready made slipcover, it's odd but pretty plain. Anyway! I've watched enough trading spaces in my day to recall them just throwing a sheet over the couch, pinning it all around, sewing where they pinned, turning it right-side-out, and slipping it on. Is it as easy as they make it look or is there a better way to do this? I have this idea in my head, that I can make the "seat" just a flap (with velcro around loose edges) and then cover the cushions individually so it's easy to access the bed.
Any comments, suggestions?