This is actually very easy.
Just start a round of tournament (since rounds are based on death, not time). It doesn't matter how many players, but less makes it easier (I was still able to do it on a 4 player match).
Once the round starts, pick up the controller for the other player(s) and press RT, RB, LT and LB at the same time. This will cause the other player(s) ship to self-destruct, killing them instantly.
Just keep this up until you get the 10 matches.