Surrealist Techniques - Decalcomania and Beyond
Check your Workbook for more information on the Surrealists, a fascinating group of artists that gave us loads of astonishing techniques.
Frottage can be created by using other things for texture as well. You can even use Collagraph plates as textural elements under the paper in a Frottage-like fashion. See the Parsemage and Printmaking video for information on Collagraph plates.