Making outside corners rounded on a drywall application instead of square?

Instead of having square, 90 degree outside corners on my finished drywall, you know, with outside corner beads, I'd like to try and have the corners rounded. Does anyone know of a technique for doing this that won't be too time and money consuming? I'm not talking about having an archway, I mean that I'd like to have the vertical corners be rounded. I'll have both 4 and 1/2 inch thick walls as well as 6 and 1/2 inch walls.