Maybe it was just the fitting on my cheapo mini gun. It came loose, but I had to really pull. I don't think the grease should clog it, that's what it's designed for. I don't know about the shroud. It seems that marking it and cutting a small hole to access the zerks is a good idea. I have the aluminum Zspeed one so I have to completely remove it to get to them.

 

Think of teflon tape, but heavier duty. Wrap the bar with it a couple of times, extending to about 1/2" on either side of where the bushing falls in place. Apply the grease on that before putting the bushings on and assembling everything back together.