If there is methanol dissolved into the water, that should make it easy to blow out the water/mix.
Just do it outdoors and away from smokers..
I would also take grounding precautions, to insure no
static electricity sparks could make it a bad day..
I wonder if there is a risk of frostbite too..?.
Note: I'm no expert at explosive gas venting.
Doing this without understanding what you are doing, could get you killed.
Any of the propane that is vented will go right to the lowest area of the ground, and accumulate.
May be good to do this kind of thing on a windy day..
And,
"Once water layer has formed, diffusion of water into liquid propane is so slow
that even if propane warms or is replaced by drier fuel, water will not readily go back into solution,"
this factor would also seem to help with flushing out the water..
Left upside down during a really cold night, and allowed to warm up
a bit the next morning, (before venting) should still allow the
removal of a large amount of liquid water.