I'd recommend doing the "fake" multiplayer glitch for this trophy, which you can find how to do here: https://pastebin.com/Jgf6vPeJ
Before starting the round, make sure you vote for the Snowball version of Tumble in the vote menu. Alternatively, when you're creating the round, go into the Settings and set the game type to Snowball only.
This one is fairly easy to do (even though it's the rarest Tumble trophy, for some reason). Simply aim at the other player and keep shooting snowballs at them. Make sure they don't fall off of the edge into lava, however. Once you've thrown enough snowballs, the trophy will pop.