Hi Lilyh,
I've tried the same in share ce3.2 today, based on that other article you already found and on the dublincore example. Here's what I did:
1. add a new aspect aspect in contentModel.xml (see dublincore)
2. add the new aspect in the add/remove features action (web-client-config.xml)
3. edit web-client-config-properties.xml to show the new aspect properties
4. add the new aspect in share's 'Manage Aspect' list (aspects.get.config.xml)
5. add the extra metadata elements in the detailed metadata view (web-framework-config-commons.xml)
This seems to work for me, but make sure you have backups of these files.. As of yet I haven't found any clear documentation as to how to safely extent for share in the same way as you would do it for Alfresco.
Cheers,
Kris