I found another method for non steam custom skins
Its almost same download from css.gamebanana.com than u get win rar extract to file not win rar and then just paste it in custom. SoadY1991 is a little bit hard i tried no luck then i tried this method like. u install ct winter urban u get winrar follder then extract it to a file and just copy it to custom folder like this.
counter strike-----> cstrike----->custom and paste it there. I know my method is not clearer so heres the link to easy way if not understand me
PS: This method works on all versions steam and non steam
PPS: This link leades to paste in materials but paste in custom folder