The very first thing you *must* do is make sure that the rod screw is straight.
The big trick is to pinpoint where the bend actually is and in what direction it goes. Sometimes you can figure out the direction by looking at the end of the barrel (hinge tube) with the rod inserted - you'll often see that it's pushed over to one side.
I'm assuming you don't have a press so will have to use pliers (with protected jaws...cardboard is usually sufficient).
My approach to this particular key would be to insert the rod screw from the far end of the key, get the pliers on the touchpiece arm and apply some force in various directions in an effort to see if any of them allow the rod screw to slide in further. The tricky bit is keeping a pushing force on the rod while you bend the arm.
One little tip is to put the pliers in a vice - which then gives you much more control and allows you to get another pair of pliers on the key while pushing the rod screw in.
At some point you often have to take a punt and bend it one way or the other - and hope that you're not dealing with an S bend.
If you can get the rod all the way through, even though its binding on the barrel, it's often easier to fit the key to the horn and do the bending in situ.
There is another method that uses an slightly undersized rod with a gentle bend in it, which is driven through the barrel with a drill. As the rod is spun through the barrel it centres it up. The drawback is that it can expand the ID of the barrel...which requires other techniques to put right.