I have a one gallon Blitz can, the ventless one. Well, plastic can. It's not that bad. Works well enough for filling up my push-mower.
I used to use three 5 gallon diesel (yellow colored) Blitz can on a regular basis. [I would fill up my car on B20, then fill up the three cans. It was at least 15 miles out of my way to get B20. So, when I would go, I would stock up.] Holding 5 gallons of fuel, while waiting for it to drain into the tank on my car, got old, real quick. So, first I took a sheetrock screw, and screwed it in, right where a vent normally would be.
Wasn't quite enough. So I got a 3/8 drive hex wood screw, and screwed that into the hole I just made. That is big enough. After putting it in and out a couple of times, it's easy to do by hand.
Maybe you can do likewise on the Blitz cans.
B20 (and D2 for the matter) really don't need these stupid vent-less cans. But that's just venting on my part...