The following is a pretty common strategy for the Challenge Championship which has been used by a lot of members of the Discord who know about it. It’s a pretty cheesy strategy, but works very effectively bar against a few problematic trainers. Feel free to ask any questions or struggles with the game in the #help-and-questions channel of the Discord if you’d like as well. Credits to A_Wild_Noob_Appeared for the strategy :>
The strategy involves using Entrainment first turn with Durant, and then hard switching into Delta Arcanine and alternating Protect / Swords Dance with Truant turns, then sweeping with Extreme Speed / Earthquake. Delta Blaziken provides great cleanup if Delta Arcanine ever goes down.