The quickest way to practice is probably against the .target, offline. This will simulate a target flying at the same speed as you. Once you can reliably predict and aim the rockets against that, you're all set to find a formation and set yourself up behind them at zero relative speed, and simply fire away just like with the .target.
An even more effective setup could be to find the right distance from a head-on approach (it'll be much further and you'll have to keep your approach speed the same while testing different firing ranges) and then making a pass shortly after that. It could make for a single pass kill on the whole formation.. Especially with a 110G's 4 WGr21s and nose guns.