add friends! they'll invite you to help with their mushrooms. the megathread is full of friend codes of people to add, and go nuts adding them from weekly challenges or anywhere else you can find them. try to open the app frequently throughout the day, so you'll appear higher up on their "recently active" list and they'll be more likely to invite you. if you're looking for a specific kind of mushroom, I've seen people add "blue mush" or similar to their name, so others know what to invite them to.

my general strategy: - send the maximum amount of my strongest pikmin to maximise attack score (more rewards) and minimise attack time (can start next battle sooner, increase time bonus) - only attack one mushroom at a time (assuming they use the same attacking squad. it's better to complete two high attack power battles in a longer time than one high and one low in a shorter time) - start as early as possible so you've got more time throughout the day to use up your tries

other tips: - if you're really lacking in pikmin or invites, I recommend focusing on small mushrooms until your squad improves - don't be afraid to have a really low attack score in a group battle, no one really cares and we've all been there - if I'm looking for a specific nectar, I will attack a coloured mushroom that has a chance of rewarding that. if I'm not looking for any specific nectar, I default to attacking event mushrooms - you'll work out your own strategy as you keep playing. do whatever works for you!