How do you change shaymin into shaymin sky form on pearl?

I think that shaymin's forms are exclusive to platinum as they require a giveaway from a Nintendo event. If it wasnt built into platinum pearl/diamond then you wont be able to change its form. It would be like trying to trade across Pokemon to lower generation games which don't support that Pokemon. If the method for doing it in platinum doesnt work then you simply cant do it.