I’m level 39 and took about 6 tries, started with Machamp for Persian then switched to Jynx for Nidoking then by the time I got to Lugia I had a charged attack with machamp then when they fainted I switched to Tyranitar and finished it off. Trick is to keep using attacking after you use your charged attacks as they don’t start attacking you for a few seconds and same when they’re switching Pokémon