So you want to use CForm (form builder), but need to preload dropdowns in a form? It's simpler than it seems.
You got your CFormModel, CForm and the actual Form, right?
Let's say you have the typical State -> City dependent dropdowns, so you would want to load the from with the State and City selected.
It is convenient to use the same identification attribute, say info, in all of the active records of your application. It should be a virtual read-only attribute defined by a getter method, its label being the model name.