[X] Staryu's Idea - Rapidly moving between isolated Team Rocket trainers with only one trainer pausing at any given point, this will be an exhausting, high-speed endeavor. But it'd deal considerable damage to Team Rocket as a whole.
[X] Pineco's Idea+ - Observing the Team Rocket trainers from a distance and organizing less experienced trainers into a movable picket would mean relying on inexperienced trainers. But if it works, it'd completely shut down the ability of Team Rocket to move forces through the mountains. Willow will stay near you to act as a rapid reaction force for any potential breakthroughs alongside your own team.
[X] Violet's Idea - By combing the mountains carefully, you can isolate 1-2 Team Rocket trainers and attack them with overwhelming force. Safe and straightforward, it's almost evil as to how unfair it is.