My method of pouring powder out of my flasks consists of putting my index finger over the end of the spout, inverting the flask so its spout is pointing down, pushing the gate lever open with my thumb and holding it that way while I rapidly shake the flask back and forth 5-10 times. It only takes a few seconds.
Then after releasing the gate lever, I'm ready to pour the powder into my brass measure.
Most of us old timers all agree you don't want to pour the powder directly out of the flask measuring spout directly into the gun barrel.
I've never had it happen, but it would only take once for a glowing ember in the barrel to set off the new powder charge directly into the flask.
Now that would ruin your day , Ah says. ::