That's weird — I use the hummingbird line also
Firstly, let's just ascertain how 'angle-specific' the pass actually is...
There are numerous occasions when the pass should NOT be used, and one of those occasions is if you're stood, your specs are sat.
Also—most passes I've ever seen are indeed sloppy. But as mentioned, on an offbeat or misdirection, the pass can work fine.
However, the 'utility' of the pass is easily achievable in other ways, such as a double undercut.
Learn the double undercut, and if you're caught with a break above a card and can't use a pass, simply double undercut. You won't have to worry about passing the deck.
I practiced for ages trying to use the pass as a colour change, before I used it to return a card to the top etc. and this practice helped me realise the 'masking' moves of the hands.
Mirrors will help. So will 'allies'. It's all about practice, as usual. And as the first post mentions, the sloppy passes are rarely noticed by laymen (and for a bizarre pass, check out Sadowitz - to a layman, it looks like a card juggle, but his pass is SO obvious to a magi!) and yet magicians usually can tell.
Offbeats work fine - and possibly the finest pass I've seen is that of Sankey - who uses his '1-2-3' rhythm and beats to CREATE an offbeat to pass the deck.
It's a matter of first learning the mechanics, then adopting the method to your own style and hand size, and then practice. Books alone may not be enough here - you need to audience test it with a friend etc. first. You simply can't see the bad angles on this as a performer.
Another tip is to pass the deck at waist height. I've seen many magi perform 'dodgy' passes higher up, and I've also seen magi's trying to disguise the pass as a flourish - which is a terrible way to arouse suspicion after having a card returned etc.
The whole idea behind the pass is for it to be barely noticable - which, if done correctly, can look as innocent as simply squaring the deck.