in double battles you can turn him into a nigh unstoppable wall by having a team-mate soak him. This reduces his weakness from 5 types (flying, rock, ghost, fire, and dark) to 2 types (grass and electric) making a whopping 15 types completely useless against him.
I try and place him in comp team cuz he's so awesome, but it gets shit on no matter how I try to work it. I'm sure Smogon would rather have him banned, because when soaked pretty much all of their precious meta-game goes out the window.
For actual build though I like to use Shadow Sneak/ Mud-Slap, Sunny Day, SolarBeam, and aerial ace, obviously he's a part of a sun team and putting sunny day on this bastard makes it a nightmare to remove. If you use Mud-Slap instead of shadow sneak you hit 6 pokemon for 1/2 damage, 250 for 1x and 413 for 2x or even 4x, it's got better coverage vs. priority, your call. If you take off sunny day and use Sunny Day that now becomes: 1 for 1/2x, 193 for 1x, 475 for 2x or 4x, but you lose sunny day brute forcing
