Once you've updated godaddy to point a domain's name servers to dreamhost, you don't need to update there again to add new sub-domains. Just add them in the DH panel and you'll be good.
Propigation of DNS info can take up to 72 hours to complete. If you'd like, you can post your domain name here and other users can see if it's pointing to DH yet or not - from our locations.
art.googlies.net - personal website