each model has texture paths.
eg. bob.mdx=bob.blp+sword.blp+shield.blp
etc
and when they have the same as diff mdx but same blp, they override.
Convert the mdx's(models) to mdl using yobguls converter(dont panic if it comes with errors, its a buggy tool) in the tools section.
then open the mdl(was a mdx)with notepad and find something like this near the top of the data.
Textures
"Katana.blp"
etc
Change the name of Katana, to something else. like katana1.blp.
then save, and convert it back to md using the converter.
now go to the models skin, which should be Katana.blp, and rename it to what you typed in the mdl, Katana1.blp
Open all the other models and do the same but instead:
katana2.blp etc and rename their skins to match.
sorry, i cant explain it more clear.