you can go to the autoparts store and find a tube of Lubriplate motor assy. grease. Its around $6-8 for a large tube. Dope up the plug and just reinstall it and tighten it up *finger tight*
Now i also would take down the rifle and get some Flitz Polishing compound. It protects the steel from rust for up to 6 months. Take off the sights and pretty much whatever you can get off safely and rub it down in this stuff then buff it off. Makes for super easy clean up.