Source.Python forums

can we set the arm model for csgo??

http://csgo.gamebanana.com/skins/133419

comes with arm/hand model but not sure how to use it

AFAIK this falls under setting weapon viewmodels, which I don't think is impossible but it isn't easy either.

But since you're using CS:GO you should probably try using .kv files, they let you have custom hand models (or materials only?) per map, but only one per team. They also allow you to have multiple player skins per map.
For a tutorial: http://csgo.gamebanana.com/tuts/11054, this is entirely build-in into CS:GO.