I always use petroleum jelly / Vaseline when building my motors. Rod bearings, crank, wrist pin, rings, piston skirt, bore, block bearings, both cam boss, cam lobes, and even on the crank threads to tighten the flywheel nut.
It keeps all the parts greasy, and prevents dry starts and wear.
Example: If you start the motor without oil by accident, and run it for a minute. Kids do that all the time out here. It stays greasy until it gets hot then it melts to oil.