how do you make skins for group01 models

i want to make a bunch of skins for the HL2 group01 models but i don’t want to edit the original .is it easy and can anyone tell me how or give me a guide on how to make them.
I want to make it for my garrys mod server

If you want skins that don’t overwrite the original model, try hexing.

I have read this before and failed on setting another skin. did you or anyone know a tutorial or can give me an explanation.