A vert pro that I know said the secret is learning backside ollies first, then backside airs will come very easily as you know how to land already.
Also it is not so much you ollie on vert or bigger ramps but more just roll up faster than you would to kickturn lifting the front of your board and let your back wheels bonk off the coping, but it is good to learn to do backside ollies on anything first, even just banks or mellow transitions and work your way up the ramp from lower down.
Another guy I know learned them really well over hips and could tweak them out and everything, but still was not so good on straight walls, but that is another option, similar to flyouts that kids do with all manner of tweaks.