Jimmy. The floating firing pin and channel is what must be cleaned well to avoid the slam firing. Get that cleaned well you will have no problems.Plenty of videos out there on taking cosmoline from SKS's. Just search you tube and watch a couple videos and you will be fine.

Jimmy, it does not have to be squeaky clean but I recommend disassembling the bolt and soaking it in mineral spirits to clear all cosmoline/gunk from the bolt / firing pin channel. Cheers and stay safe!

Cosmoline can cause a variety of malfunctions, I would clean it as beat you can and get a good lubricant on there to protect your firearm going forward, Balistol works well to remove Cosmoline and also acts as a lubricant and protectant.
Iraqvet8888 has a good video for removing Cosmoline
https://youtu.be/HXfw1bPJ0Zo