Most any type of grease is ok on the latch, just don't get carried away like gamo did, just a thin film of lube is just right.
Give the barrel a real GOOD cleaning to get all the gunk out . A lot of guys use Goo Gone to clean barrels up, I have used it and it works quite well.
The rest of the parts sholud be lubed with molly lube, you can get molly 60 from a Honda Motorcycle shop, they use it for lubing suspension parts.
It kinda expensive from there, like 13 bucks or so, but it will last a lifetime of rifles.