re: Gas and diesel cans that pour out fast and don't spill?

Buy some of those plastic yellow vent caps that go into the back of the can. It's like the old school cans had. You can buy bulk vents on eBay. Drill plastic can and pop it in

Did this last summer. Fixed my five gas cans, gave a few to my son, gave a couple to my neighbor. Still have a few left. Makes a world of difference.