Each time that you attach an energy with Rain Dance, you are using the power again.
What you did the last time you used the power has nothing to do with this time.
Most players are confusing themselves with the shortcuts they are taking.
You're not attaching 3 energy cards at once with one use of the power.
That's a shortcut.
You're using Rain Dance. Choosing a Pokemon. Attaching an energy card to that Pokemon.
Then, you're using Rain Dance. Choosing a Pokemon. Attaching an energy card to that Pokemon.
Then, you're using Rain Dance. Choosing a Pokemon. Attaching an energy card to that Pokemon.
Then, you're using Rain Dance. Choosing a Pokemon. Attaching an energy card to that Pokemon.
Then, you're using Rain Dance. Choosing a Pokemon. Attaching an energy card to that Pokemon.
Then, you're using Rain Dance. Choosing a Pokemon. Attaching an energy card to that Pokemon.
Then, you're using Rain Dance. Choosing a Pokemon. Attaching an energy card to that Pokemon.
And so on, as long as you have energy to place.