Answer:
The website surplusrifle.com has good information on MANY different rifles and pistols, including the SKS. Follow instructions on field stripping, and use the supplied cleaning rod and parts. If you do not have the original cleaning rod, you will need to get a cleaning rod, a .30 cal ore brush, and a patch holder. If you are shooting corrosive primed ammo (most older Soviet and Chinese ammo IS corrosive) then the bore and gas piston will need to be washed with hot soapy water.