I'm not familiar with the code either but if your style is a child of Core2 it looks like it's pretty simple to add. Looking at the source for http://www.dreamwidth.org/customize/advanced/layersource?id=551&fmt=html I see two presentation properties you needs to add:

property use medium_breakpoint_width;
property use large_breakpoint_width;

Then two strings in function Page::print_default_stylesheet() {
var string medium_media_query = generate_medium_media_query();
var string large_media_query = generate_large_media_query();

Then @media and one of the strings above being used in the stylesheet. Four times if I counted well.

Hope this helps a little at least.