I think I found it...
You just add an action to fire a custom function when a post is saved. You use the custom function to call update_post_meta()
So this is basically what I was trying to talk about on Issue 170 and 132 on the CCTM site discussion. Why not go ahead and generate page templates to display an edit/submit form. And just allow the user to send the submitted form to WP. All you'd have to do for WP is attach the necessary action to save the meta data (custom fields).
NOW you should be able to see what I've been talking about. Since CCTM already manages custom posts and already generates a page viewer template, why not generate edit/submit form templates as well? It gets the developer one step closer to quick implementation of an entire front-end for working with custom content types. The last step would be to generate code which automatically inserts the meta data.
I guess I just don't see CCTM as having ot be a complete UI package that solves all the problems for you. The way I envision using it is creating content types (modifying content types if necessary) and then generating the code to work with them from a front-end user-submission perspective.
If I wanted to have a homerun package that doensn't require me to cut and paste some code and messs with templates, I can wait a month or so and just buy Types and Views. Types and Views already does a bunch of custom content management and they are in the process of adding functionality for user-submitted front-end.