I don't express either of my dogs. They've never scooted or anything *knock on wood* so I've not seen the need to do it. They have firm stools so they are expressing them on their own without my help. I've also heard that once you start expressing them you have to express them on a regular basis and I don't want to mess with something that isn't giving them any issues.
This website has some good information on it:
http://www.barkbytes.com/medical/med0029.htm