I found it much easier to log in as root. I deleted all the Wacom preference files from all accounts (/User » Library » Preferences » com.wacom...), as well as the files inside
/Library/Preferences/Tablet/
. Then fire up the Wacom preference pane and set the preferences as you would like them to be. These settings will now applied system wide.
[robg adds: I would think you could do something similar by using sudo -s in Terminal open a root shell, then copy the preference files from one account to another, but I can't easily test that theory. Root is disabled by default, so if you're going to use this approach you'll have to enable it. There's a really old hint that talks about enabling root, but I haven't tested it in the last six years or so, as I've not had the need to enable root. If you enable root to do this, I would recommend disabling it again afterwards -- there are some comments about that in the linked hint.]