How to setup multisite so that subblog posts are automatically added to main sit

I’ve been looking all over for this answer but alas to no avail. I’m using wordpress multisite as magazine sections. to ease clutter of the features. Each site houses a section of the site.

Does anyone know how to automatically set it up so that all the sub blogs post show up on the main blog WITH their thumbnails?

Currently WordPress MU sitewide tag plugin send the posts but not the custom field images.

I’m not afraid to hard code but I don’t know how to set it up as such.