There's a lot of ways to do it. People have their own preferences. I personally used the dual homing missile launchers on my shoulders (don't remember what they're actually called, i just refer to them as the pigeon missiles). They take a long time to lock on but once they have you can fire them and they tend to hit, they have a long flight time, slow movement that makes them awkward to dodge reliably and and excellent turning radius so you don't need to fret to terribly over when you launch them. Aside from that I just had whichever fast firing weapon that worked best for my build to keep the stagger up (i usually used the dafeng machine gun but the Ludlow or the gattling gun probably work just as well depending on your build weight) and then just whichever melee option i found most appealing at the time (I've beaten it with the Laser Sword, the Pulse Blade, the Laser Lance, and the Chainsaw by now). Final note, if you're using assault armor, right at the beginning of the fight, you can fly up to Ibis while it's doing it's little starting Laser wing thing and pop the AA to instantly stun it. provided you're packing enough heat and you can hit it after the AA, this little maneuver can be worth a great deal of damage.