This is my own playthrough Basically, you get near one of the shielded pylons and then aim your vehicle at the next pylon you want to go to. As soon as you see the red circle on the ground, jump up and hit speed boost to get the hell away. Let the cannon take out the pylon for you. I had problems the first time I played because I didn't understand what was going on. But, with some practice it becomes relatively easy. Just keep an eye out for the red targeting circle on the ground and have your vehicle already pointing in the direction you will go when it shows up.
As you were replying, I figured it out...it's frustrating as all hell, though. For me: kept moving out of it's targeting triangle, mines showed as yellow lines on the ground. it doesn't matter how high up in the air you are, if you're in those parameters, you get blown to bits. A lot of moving around and yeah, firing close enough for the blast to take out the generators as you zoom away. As for the final round against the gun itself after the barrier is down, kind of the same process...firing close up, then when it targets you, speed away and its blasts destroy itself; three of its own blasts will kill it.
But thank you for trying to help. It bugged the crap out of me. Definitely one of those moments you have to have a LOT of patience for and can't already be a little irked.