As for DSON, if you don't already have a copy set up  in Poser 11 it will be impossible to learn it because It is no longer available from DAZ as far as I can tell.  After the Python upgrade in Poser 12 and newer, DSON isn't supported by Poser either.  BUT, if you have P11 and a copy it will allow you to load some Genesis and Genesis 2 content pretty easily.  With finagling you can load more recent DAZ content, too.

I'd go with Chromestar's advice and learn to import FBX props and clothing which can be made to work in a number of ways.  Beside Sketchfab, I also go to CGTrader for material.  There's also some Poser material at Renderhub but they don't make it easy to find; searching using the term "Poser" brings up some pretty good stuff.  If you like kinky science fiction, steam and dieselpunk, look for a content provider at Renderhub called Jibicoco; he shares a lot of cool stuff that is completely Poser compatible and FREE.  XD

Teh Mollz