perhaps it was more him flying through your sights and not you maneuvering into position. 
It may very well be. However, it is the maneuvering itself that is important - IMO. If you're able to smoothly move from one maneuver to the other in combat... gun solutions will produce themselves without you worrying about how you'll make a super move for the next shot.
W7LPNRICK, I went ahead and tested out the Spit IX's snap rolls... it does seem to want to spin quite a bit if you put too much english into it. Just try to ease your way though the rolls with a bit of rudder and elevator backpressure... and like TC said - reverse aileron at the desired bank angle to stop it.
NOTE: In of itself, the snap roll probably isn't considered ACM... it's more of a component of it. I use it only if I remember to and usually if I'm trying to shake a bandit lodged on my six while in the middle of some kind of scissors. I wouldn't recommend relying on it to bring you gun solutions (although in some extreme cases... it does!). I find that co-oridinated rolls using RUDDER and reducing the G-load on the wings during the roll (not pulling hard on the stick) can get you over to the desired angle of bank quick and smoothly.
Not to say the snaproll shouldn't be used... practice it and keep it in your back pocket for those dire situations where it can surprise people. Don't get frustrated if it's not easy to do at first. If you get stuck take some time and schedule an hour or two with a trainer - some of the most patient people in the game - to work on it and maybe help you on WHERE to use it.
Good luck with everything,
Cursed