in fact it is easier to swing on no bend because when it does bend, you can swing easier but only until it starts recoiling, and by then if you arent in line with the pole you wont swing any farther. Like above, just practice swinging all the way back on a straight pole as fast as you can with a long straight trail leg. Another key point most people miss without a coach is that to be vertical you cant just swing your legs so they are straight with the pole, you need to get your hips directly above your shoulders. This usually means beings your legs PAST perpendicular with the ground when you swing.
In lamens terms, swing like you are doing a backflip, until your hips are above your shoulders, then start to straighten out with the pole.
Once everything is controlled in a pop up (straight pole drill) then go to a 4 step as said above, with a soft pole. Then you need to concentrate on MOVING the pole, as they say. But this is describing the motion after you are vertical with the pole, in which you move your hands up (or down, literally) toward your head, with as much pressure down the box as possible.
You technically need to get your top hand moving past your hips to jump over your hand hold, because when you turn your hips will be a little above your peak hieght.
This might seem really complicated, but watch any of these videos in slow motion and read each part of the vault i describe and it will really help you to understand.
Thats how i learned
http://www.stabhochsprung.com/
any questions just ask, i love talking about this stuff!