Omega 4 css for responsive design, where to do what?

Hi,
thanks for all the work with the omega themes, I have been using version 3 quite succesfully. Now I wanted to work with omega 4 but I got completely stuck.

The main problem is I don't know where to place the device specific css definitions.

I learned about susy and sass and the compilation and inclusion is no problem. I built on the ohm template and thought I could simply add my device specific commands in three different files and import them in the layout scss file inside the specific breakpoints, but imports are not allowed inside media queries.

Then I tried placing the media queries inside the files to import which got me a bit closer. But I realized that the layout template css is called first, so base and the ohm css definitions overwrite them.

Afterwards I thought I could create the device specific definitions in files in the main part and simply add media queries to the specific files. But this does not work either unless I copy the whole layout definition and import susy again into a file outside the layout template.

So now I'm lost. How are we supposed to do it? I have several definitions that have to be read in for mobile, tablet and wide formats and have no more clues on how to tackle this.

Any help on how to use omega 4 with responsive design and separate css files for different devices would be greatly appreciated, I have tried the documentation, the irc channel and drupal answers with no real luck.