There is no need to lube the bolt. A tiny teeny weeny amount around the rubber bolt tip wouldn't hurt, but the rest can be left dry.
The only point on the bolt that does need lube is in the little hole in the centre of the bolt insert stem right in the back of the bolt. This slides over a part of the poppet that has an o-ring on it so it does need, again, a very small amount of grease.
The main thing is that the bolt guide and particularly the bumper and the back face of the bolt are kept nice and dry so that the bumper doesn't stick to the back of the bolt.