A good competitive cocancer set

[uredi]

Hello there, i'm new on strategy so i think you could help me

So here it is, i wanna building a cocancer as a stealth rock setter, and definetely stall, it méandres with toxic, stealth rock and infestation, but i'm asking myself for what would be the best 4th skill, between Sunny day, synthesis and wood Hamlet

Well, let's try to make it clean :

Hability : harvest

Item : sitrus Berry

Skill :

Stealth rock

Toxic

Infestation

Sunny day/synthesis/wood Hammer

Ivs : 252 def, 252 SP def, 4 HP