Okay I imported some hands onto my human model, joined the meshes, and welded the vertices together. Everything is nice and neat…and connected. The only thing that seems to be wrong is that when I do any kind of texturing to the mesh, everything is textured or colored except the hands. Without texturing, the hands are a darker grey than the rest of the mesh. I find that deleting the faces and remaking them solves the problem, but that takes ages to do each face. Also, I began modeling clothes into my model and the same thing happened, except this time only the new faces were textured instead of the entire mesh. I have attached the blend file if any one wants to take a shot.
I took a look at your blend.
The reason your hands are not the same material as the rest of the body is because you have the vertices for the hands assigned to a different material. To add the hands to the rest of the body in your material index, go to Edit Mode, select all vertices, make sure you have material 1 (Mat 1) selected in your Links and Material panel in the Editing button window (F9), then select assign.
It looks like material 2 is assigned to the hands and material 3 would appear to not have any assignment. You could delete materials 2 and 3, unless you had plans for them.
I tried to do what Soter said, but it didn’t work. I started exploring around that Links and Materials and found a delete button. I commenced to clicking it, and I deleted all the mats. As soon as the last mat was deleted, that dull grey color left the hands! WHOOHOO! I colored it and rendered it just to see, and it worked! Thanks ya’ll!