Updating the buildd code
Ask lamont to update the appropriate builders. Generally, you will want to test on staging or dogfood before deploying to production.
Updating bzr-builder
bzr-builder is installed every time a recipe is built, so you only need to update the relevant archive, and subsequent recipe builds will use it.
Dogfood
Launchpadders have access to the bzr-builder-dev PPA. Just upload to it.
Production and Staging
The production and staging build farms use http://archive.admin.canonical.com/ubuntu, with "cat-lpbuildd" as the pocket. Once your packages have been tested in dogfood, get Elmo to copy them there.