[Plugin: Press This Reloaded] Fill costum fields with parameter values

I am not using the plugin itself, but it gave me the hint, how to open the new costum post type site just by adding the new parameter “post_type”.

Next thing I want to do, is to populate some costum fields with values given by some other url parameters. I can not find any hint for this in the forums, so I am posting it here, because it seems related for me to the topic of this great plugin.

Do you have an idea for solving this problem, scribu?

http://wordpress.org/extend/plugins/press-this-reloaded/