I don't know if I'd use a whole lot of heavy grease, I've read where some guys have had a problem with it plugging up the oil pump screen. It just doesn't seem to want to break down and mix like you'd think it would. I would clean the cam within an inch of its life and then massage it with the black molybdenum disulfide that comes with the cam. Here's a cam break-in procedure that I follow.
CAM BREAK-IN
Anyway, use only stock springs to break in the cam, changing them to the springs you're going to run after you have several hundred miles of easy runnin' on the motor. Fill the crankcase with racing type oil that has sufficient zinc content to protect the cam. (Read the article in Car Craft March 2006 concerning the removal of zinc by the oil companies). Add one bottle of GM Engine Oil Supplement, available at any GM dealer. Prime the oil galleys. Adjust the valvetrain and spark advance so that the engine will crank right over. Bolt on a carb that is primed with gas and ready to run. DO NOT, REPEAT, DO NOT GRIND THE STARTER TO START THE MOTOR. IF IT DOES NOT START RIGHT AWAY......STOP!!!!!...... FIND OUT WHAT IS WRONG. While an associate monitors oil pressure and water temperature, bring the r's up to between 2,500 and 3,000 and hold it there for 20 minutes. Shut down, replace oil, filter and GM EOS. Run easy for 300 miles. Replace oil, filter and springs. Enjoy.