for example, a boot texture...
double the size of the original texture, unless it's a chest texture, those just get too big and lag too much. take your original picture of a boot (try uscav.com) and drop it on top of the old one, make it 50% or so transparnt and match the size. take yer time, be conscious that the texture may have to be distorted somewhat to work correctly. You won't lose too much detail if you resize your original texture to as close as possible before dragging it over. I have found that if you use "free-transform" to resize, you'll lose a little more detail since it's usually a few steps of resizing before you get it how you want it.
For chests, etc, I lay the pieces on top and try to match position, and do a lot of erasing with the airbrush tool, and color/hue/saturation matching to make it look like it's one vest or whatever. many times I get the torso texture ts from 5 or more originals! Practice, the true reward is in the details buddy.
