I've finished texturing the horns and refined the face with a paint-over to create definition and interest. I now need to go over the Giant's body with a similar paint-over to further refine it and then take everything over to Maya to begin rigging.
I've had a hard time figuring out the Mudbox > Photoshop > Mudbox pipeline but I've finally got it all worked out and am making quick progress with my Giant model using photo textures, both in Photoshop and as stamps in Mudbox.
These are only screenshots taken in Mudbox but I'll be applying the textures in Maya and running some test renders soon.