Hello,
When you initially receive it, it will likely have a thick brown grease covering it.
I like grease cutting detergent like Dawn and others, along with hot water, to remove this.
Afterward, clean and oil thoroughly.
As for the stock, wrap it up in newspaper and set it on a heater or even put it in a car trunk during the summer. The cosmoline will sweat out. The rest will come out as you shoot it, so keep a roll of paper towels handy for the first couple range sessions.
If you are shooting military surplus, realize that the primers produce potassium chloride, a salt, when they ignite. This attracts moisture and will cause rust. You must clean right away.
A good cleaning as you would normally give it is all that's usually required. However, some folks feel better using a bit of soap or Windex first to clean the salts. (You will hear that Windex somehow "neutralizes" the salts; this simply is not true. It cleans it out like dishwater would).
If I feel the need to put water down my barrel, it's a patch soaked in dishwater followed by a patch or three dipped in regular water to rinse the soap as soap left on will cause rust, too!
After the initial cleaning with hot water to help dissolve the cosmoline, do not use hot water. Use tepid or cold water as hot water will cause flash rust.
Be sure to clean from the breech, and don't over clean. I've seen more guns cleaned to death than shot to death!
Regards,
Josh Smith
Smith-Sights.com