My boyfriend uses this when we go clubbing as it's much easier to dance in, but he's fairly large chested and it's hard to get a satisfying look out of it.
From what I gather, it's really tricky to use for busty guys. We needed a lot of tape and an army of friends to wrangle em into place, and it works for the purpose, but also he says it stretches the skin over his sternum something fierce.
It can be easier to apply laying on your back, as that let's gravity move your chest over to the side and compress it a bit to start off. Also tried bending over while applying the first piece to try and get more "hang" to maneuver with. Both seem to help vs applying it while standing up right.
You're right to note the angled application being better, though. It might work better with more practice, but it's expensive, so we only keep it around for going out dancing.