Have you considered attending the next NBA Conference in Raleigh, North Carolina on Oct 7-9, 2011, where there will be a comprehensive tactile graphics curriculum?
The University of Washington uses Adobe Photoshop as part of a multi-step process for converting print graphics to tactile graphics intended for printing to puff paper. Dan Comden has given lectures at braille conferences about the software.
Jim Barker, a Specialist at CTEBVI, gives lectures every year at the CTEBVI conference in the spring about using photoshop for tactile graphic production.
As a braillist, I would strongly encourage you to use Illustrator or Corel Draw rather than Photoshop for preparing tactile graphics. Photoshop is really intended for touching up pictures. Illustrator is more of a drawing tool which allows you to create images and add text.
Print graphic images are usually far to complex to be directly converted to tactile graphics. They need to be simplified, in some cases, radically simplified, so that only the essential information is conveyed.