I have looked everywhere and can't seem to find any tutorials on preparing images, specifically t-shirts. I am well versed in photoshop and illustrator.
As I understand it I need 2 images. One semi transparent? One flat solid white? If that's correct, when doing this and adding the color black #00000 the shirt turns dark grey not black. What am I missing here? Is there a tut on how to properly prepare the images?
The shadow layer (the mostly transparent one) can not contain any white anymore (unless in a few select areas for highlights). Your shadow layer still contains some white everywhere, that's why black appears grey. You'll need to remove this. Gimp has a handy function for that called color to alpha, last I checked Photoshop did not have that, but I'm sure it also has some way of doing this (color channels maybe?).