Last week I was browsing through some art books and found (and bought) this very interesting one:
Title: The PASTEL BOOK - Materials and Techniques for Today's Artist
Author: Bill Creevy (1991)
Publishing details: Watson-Guptill Publications, New York ISBN 0-8230-3905-6
In fact, the reasons I was drawn to the book were the exciting sections on pastels with mixed media, in particular the sections on using Soft Pastels with Acrylic Gels or Modelling Paste, Oil Pastels with Acrylic Medium, and making Pastel Monotypes.
Since buying the book I have had a brief try with Acrylic Medium over Soft Pastel but admittedly without much success ... so I feel that this may take a while to conquer! But I did manage to produce the following in Oil Pastel plus Acrylic Medium: