Rhydon raid

I'd aim for at least 4, but you could probably do it with 3 in a pinch.

Try and use something with water or grass attacks to take advantage of those double-weaknesses. A good Machamp also works well.

If everyone has like 3 or more level 30 vapes, then I think 4 is enough. I've done one with 5, but that involved twister gyarados etc.

My PokeBattler-Simulation and my first and only solo-try implies, that 3 Players over level 35 should be sufficient.
With 4 Players, no one needs to go with a second set of 6 Attackers.