[ithacaartist]

One could also use a dense hardwood. Less expensive?

Technically, you won't necessarily wind up with true roundness by pressing, as the edges/ends of the deformation will not totally conform due to "spring-back", but it will probably be close enough. It might save a lot of effort to use a hardwood internal mandrel and another piece of hardwood to tap down the apparent high areas from the outside. This lower-tech approach is an art, however, done by someone who can feel the progress.