Well, rest on accelgor is a terrible idea as he has a 80/40/60 bulk. if you need a good special attacker with rest and hydration, manaphy is a good idea. Give manaphy this moveset:
Manaphy @ Leftovers
Trait: Hydration
EVs: 4 HP / 252 SAtk / 252 Spd
Timid Nature (+Spd, -Atk)
Tail Glow
Rest
Ice Beam
Scald / Surf