I have very little experience with creating Poser mats, but...

"Create Poser Mats" plugin for DS3 (I'm not sure if it works in DS4) can be useful:
http://www.sharecg.com/v/36622/Plug-in/Create-Poser-Mats

It isn't perfect and you'll probably need to adjust and re-export the mats from Poser to get them to look right, but if you've already created your DS mats in DAZ studio, the plugin will make things easier for you, not having to manually look for for the texture files in Poser.

And here's a very clear, simple tutorial on how to convert MC6 material files (at least Poser 9 only seems to export MC6 mats) to more compatible pz2 MAT poses: http://forum.runtimedna.com/showthread.php?43996-How-to-make-a-MAT-Pose-file