Unfortunately there isn't a built-in way of doing this automatically. I personally just do it manually - first runnng `python manage.py sql bundle` to get the column details and then using ALTER TABLE to create the column (possibly changing the constraints or adding a default value if necessary). Granted, it is annoying to have to do this every time. There's a Django app called South meant to make this process easier, if you want to look into it. I've only used it once myself and never really got into it (just found it a bit difficult to use), but I've heard good things about it. Let me know how it goes if you decide to try it.
I'm using it at work and it's actually pretty easy to use, as it can create migration scripts automatically.
Michael.