I've used Smeargle to pass Shell Smash. I run Jolly with max HP and Speed. I use it as a lead, then send out something good like Mewtwo or Arceus. Sometimes I'm able to pull off 3 smashes, and get lucky with how long Spore lasts. And since I have a White Herb, I don't care about the defensive drop so much. If you can pull it off, it works AMAZINGLY with any ATTACKING Pokemon. If you're using Moody with Smeargle, be ready for anything to mess up. You could get a +2 boost in Sp. Atk while lowering your accuracy a stage. But then again... you could pass max accuracy and evasion... but that would take a LOT of luck.
Let's just run the numbers:
Each stat has a 1/7 chance of being raised by 2 stages. Then, a different stat has a 1/6 chance of being lowered by 1 stage.
Let's just say you were passing to a Mewtwo. If you're using Shell Smash 3 times, with a White Herb, that means +6 in Atk, Sp. Atk, and Spd at the cost of -2 in Def, and Sp. Def. Let's just say you want a +6 Evasion boost, and want anything but Sp. Atk, Spd, or Accuracy lowered.
1/7 (Evasion) * 3/6 (Atk, Sp. Def, Def) = 1/14.
1/14 cubed is 1/2744, or a 0.036443148% chance of that happening.
That means that there's a 99.96355685% chance of this screwing up.
Which is EXACTLY why I hate MOODY as an ability.