the safety cans have gone so far as they are almost unusable IMO. Never filled one without a spill and they no longer have a vent so pouring out of them is a glug, glug, glug affair. total PIA!
You're doing it wrong. The spouts on the safety cans are vented so that they flow smoothly. The trick is to make sure the spout is pulled out as far as it can go (getting gas all over your hands), then make sure the vent assembly spring is working (getting more gas on your hands).
If so, pour but use the edge of the tank's opening to push the safety nozzle's foreskin back so it vents.
If the vent assembly isn't working properly, remove the spout (getting more gas on your hands) and fuss around with it until you fly into a homicidal rage and light a match to the whole thing. Make sure your gas-soaked hands are nowhere near the flames. You'll thank me for that bit of advice, BTW.