They are greesing the break pad
It goes behind the Breakpad where the metal of the pad touches The Plate. This stops the breaks from squeeking during breaking. Its also used for front Disc break shoes on the back of the pad where it connects to the Calipers. This stops unwanted metal squeeking.
Now as for the Lube. I use Electric Motor oil. Dont have a brand name right off hand, but thats what i use. Its made for HIGH rpm's.
As for guns. Its not guns that kill. If the person was going to do it, They would use whatever they HAd, Ie. Knife, Hammer, Ect. Cant blame the tool, Just the user. And Moore Is A complete Whacko! His socalled films are FILLED with miss information. All of it false.
Harry