Ok, I'm not sure if someone already suggested this, but here's what
I'm thinking of suggesting. So you know how when you go to plant
berries, and there's the trick to hold left shift to plant a full
row of the same berry? Well my idea is to expand on that feature,
but make it for watering your berries. That way we can mass water a
full row by holding left shift as well, and we can finish planting
more berries and leveling up the berry garden faster.
You unlock a new Watering Pail thing for doing something (I don't
remember) that already does that for you. So just keep planting,
watering, and raising berries and you'll get it! :>