render (:xml=>:model) based transformation

Hi,

Trying to get my head around how Rails works. I am trying to generate
an xml representation of a model's list view. It works well when I try
to simply use

format.xml { render :xml=>@models }

But I need to change the name of the elements slightly. Tried to use
an action.rxml template using the following syntax

format.xml { render :xml=>@models, :template=>'mymodels/action' }

and it seems to only generate a blank response. If I enter some
garbage in the template it gives me an error. So I know the template
is being picked up. Is there an easy way to debug why its generating
an empty response?

Another question I guess would be, is there a better way to transform
the response so that it generates what I want rather than the
defaults? render() seems to take a block. But I don't know how to use
that.

Thanks!