Why would you be worried about a move that totally heals your Poke and cures any status? Rest is one of the best moves in the game, especially when you battle competitively, when you don't have access to any of your items. If you are that concerned with the sleeping for two turns, and this is in-game we are talking about, just use the Poke Flute.
Since you don't have Emerald, Sleep Talk is out. That leaves either Ice Beam or Toxic. Here, again, is Suicune's BEST moveset:
Suicune @ Leftovers
Trait: Pressure
Bold Nature (+Def, -Atk)
- Calm Mind
- Ice Beam / Toxic
- Rest
- Surf
DO NOT use Gust on Suicune. Not only is a crappy move (40 AP), but Suicune's base Atk is only 75, meaning damage will be minimal. Also, as it was said before Calm Mind is ten times better than Rain Dance, since it boosts Suicune's SAtk, not just its Water moves, it also boosts its SDef, and it doesn't let Thunder-users beat the crap out of it with 100% accuracy.