eZ publish processes and you can see on the statusbar in the browser that ez is working, but it hangs after a while..I check some articles, Some articles have got this new attribute available, but not all.
Nope. The eZ team mentioned that I need to write a script to be able to add a new attribute on a class if there are a lot of objects of this article class in the database. Because it's to heavy to process this through the admin-interface when there's thousands of objects in the db.
As long as the process doesn't time out when you run it through your browser you should be ok. We have a script internaly that we use for this that I think you can use as a starting point. I'll ask someone who has it.