[Speedslug]

I assume you have wetted the brass with tiniest amount of a soap solution.
The stuff used for looking for leaks is perfect.
It's like 3 drops of dish soap to a cup or two of water.

Failing that a hair dryer used to warm the hose ends a little might help.

Don't use a screw or a flat bladed screw driver to stretch the hose but a phillips head might work to stretch it out enough to get it on the barb.

Of course it goes without saying that the barb needs to be in the ball park of the inner size of the hose.
Nothing quite like trying to fit a 3/8th barb into a 1/4 inch hose.
It looks like it will almost work but the odds are better you will lose more than a little skin trying to learn that lesson.

BTDT.