Bleed screw seal?

[swamp rat]

I bought a brake bleeding system and just now trying to use it, it says in the instruction manual to apply a thin film of silicone lubricant to the threads if you want to use vacuum at the calipers to pull brake fluid thru from the master.

Anybody ever hear of this? what silicone film? One person here said his dad used a bit of grease around the outside of the threads to get an airtight seal.

I have only bled brakes the old fashioned way with a helper, never with a bleeder tool.

Any help is appreciated!