I lube the neck with a bore brush dipped in powdered graphite. I don't like the idea of a liquid lube being inside the cartridge case, even if it is only in the neck.
The only reason I lube is for the neck expander. It is easier to pull the neck over the expander button if there is a slight amount of lube inside the neck.
I have never thought of using a lube for ease of bullet seating. I champher the case mouth to make an easy start, and I have never noticed damage to the bullet.
After I use the bore brush and graphite, there might be a small amount of graphite left in the neck, after neck expanding. This would provide a bit of lubrication for the bullet, but I have never noticed it.
This is for cases wiped off with a rag. I have never used an ultrasonic cleaner.
