[David]

I've never done it, but I was listening to radio talk show with a pro and a guy from Quickrete.

I assume you're using the Quickrete made for countertops.

They use rebar and recommended putting a diagonal piece across any inside corners. They use a mold and pour it upside down. They also use a shaker to get the airbubbles out, but they said you could probably get them out adequately with a rubber mallet on the sides of the mold.