no easy way...you need to cut and paste objects with the materials you want from project to project.
In 2012, you can load your own material libraries, in the materials dialog box. Yo have your own materail catalog called "my materials" that you can save out and load into another project.
Found it....
Create 3d solid in Acad, attach material to solid, then import dwg into Revit...
Thanks,
Rudy Beuc