It sounds like some extreme caution needs to be used here! As a licensed LP gas tech, with 20 years of practice, I would not be venting LP from the bleed valve. Propane will flow like water
and pool in low areas just waiting for an ignition source. I can tell you from personal experience that you will remember the experience if your vented vapor finds a spark.
The bleed screw is used to vent air from new tanks
when initially filled, and should only be done in the proper environment
LP has a vapor pressure that is dependent on temperature. When liquid propane (LP) is pumped into a tank containing vapor the vapor will condense to liquid as the pressure increases. No need to vent anything!
If you need to fill your tank from a source without a pump, set the feed tank in the sun and the tank to be filled in cold water
. Most tanks now have an OPD VALVE that will prevent filling the tank more than 80 % full of liquid, thus leaving room for thermal expansion when you remove it from the cold.
Above all, realize that if you fail to respect the dangers of LP you will likely learn a painfull lesson.
When teaching , I had a shirt that read " if you see me running, try to keep up!"