The quickest method that I've found for this achievement is to play Saucer Sumo in Party Play mode with a second controller or local friend.
At the start of the match the second player rams the barrier behind his/her saucer and then boosts off the edge using the A or LB button. During the respawn, the saucer will be transparent but once it is solid again immediately hit the boost. You'll do this seven times total per match and it will take just over 20 seconds to complete. Once you win, go right ahead and press restart to cut back on time wasted in game setup and loading screens.
By using this method you will also unlock the Winner! and UFO Savior achievements if you play on Normal difficulty.
And if you play with four controllers once during your 20 games, then you'll also unlock the Party Host achievement.