Most of my stories involve Karen McDougal. Being a brunette Playmate I like to pit her against a blonde Playmate or Penthouse Pet. I just see those as natural rivalries. I sometime use a current event as the motivation for my stories. Or I just see another hot woman and imagine what would happen if they were to go at it.
As for as research I like to use freeones.com I might see a worthy opponent featured there or just uses it to gather stats on Karen’s opponent.
For my creative juices to flow I need to have an attraction to the participants. So to answer your question I would rather stick my head in a beehive than try and visualize Rosie O’Donnell and Roseanne Barr tearing each other’s clothes off.