I think there was a PDF quick start but that was for version 1.3; we're now on 1.5.1, which is a little different.
My advice for people who just picked up PS Touch is to have a rudimentary understanding of Photoshop's main paradigm: Layers. From there, it's a matter of understanding the similarities and differences between the two.
e.g., Photoshop & Photoshop Elements have adjustment and layer masks but PS Touch lets you "paint" an effect onto a layer, even though it's destructive. (You can, however, mimic something like an adjustment mask by simply inserting a blank layer, filling it with neutral gray, setting the blend mode to Overlay, and then paint with the brush tool using various levels of black or white.)
Effects and adjustments like Curves and Levels work very similarly.