How to canonicalize XML enabled classes?

I have a registered object class that extends %XML.Adaptor and I want to convert an object of it into canonical XML. 

From reading the documentation and some trial and error, it seems like I would need to use %XML.Writer to write the object to XML first using the RootObject() method, then read it with %XML.Reader, and then use the Canonicalize() method of %XML.Writer to write it out again.

Is there a better approach?