I had the same thing going on when I first tried to open my hood, then I did what Bigass did.
Then this spring I sprayed the whole assembly with Fluid Film, and now do not even need to hold down on it
Try pushing a little harder, it can be a little tricky until you get the hang of it
It is water creating corrision in the cable. You just need to lube the crap out of it. Mine sticks too. Sometimes when water gets in during the winter.
I agree with pushing it down while pulling the knob.