This can be done using just one of the new cars or switching between them as long as you hit a total of 50 shots on goal.
The easiest way to do this is in an Exhibition match with no bots so you won't have anyone blocking your shots.
If you get the 10 goals with both Grog and Ripper trophies before this one then you should be well on your way to 50 shots on goal.
Can be completed in any arena.