>>17437109Scouting is not hard. Get hazards in, no lefties recovery, and you'll see that it's either Chesto rest or Scarf. Then it's easy. If it switches moves, it's chesto, if it outspeeds something it shouldn't, it's scarf.
Volt Switch can make this annoying, but just force it to use moves that are not volt switch.
If you have a poke with Protect, it's even easier.