The 'meta' right now to beat 6* raids really quickly is to use have one person use a bunch of boosting moves + rest using Screech/Metal Sound/cheers to not trigger the removal of buffs and debuffs and then just oneshot the mon.
The actual reality is having one or two people try that while another spams SE move, triggers a buff/debuff removal, then the oneshot attempt becomes a 40-50% hit instead, and then you finish it off from there while hoping someone didnt pick a mon that gets oneshot over and over and removing the entire timer bar on their own. Generally it works out anyway, occasionally not.
Notable mons/tidbits:
- Perrserker Steely Spirit stacks if you happen to have multiple of them. Learns Swords, Screech, Metal Sound
- Koraidon has Swords, Screech, and Drain Punch
- Gholdengo has NP and Metal Sound and is immune to status + resists most mon movesets
- Iron Hands has belly drum + drain punch and is very popular
- Miraidon has Metal Sound and Parabolic Charge
- Ceruledge has Swords and Bitter Edge to heal back to full on pretty much every hit
- Shell Bell in general is a super good item for sustain if you do not go the oneshot route because the raid mons have extremely inflated health
- If you ever host a ditto raid, it will always transform into the host (assuming imposter, no clue who it would transform into if no imposter). So pick a trash level 1 magikarp as host (and please do not turn 6* Tera Electric Ditto into Miraidon, yes i'm salty how could you tell?)
- You can use Helping Hand and other supportive moves. It's just a bit weird due to the turn order being a bit out of whack, but it very much works. You can even attack your allies if you want to be evil.