So for a single Shedinja hows this?
Confuse Ray
Hidden Power (For random status effect)
Shadow Sneak
Protect/Will-o-Wisp
Item should Be a Lum Berry or a Focus Band I think (that's the one that has a chance to survive at one Hp right?)

I dunno if its that good cause I just got one. Normally I would use Confuse ray first so he can have a small chance to avoid an attack because they are confused but that only gets me so far. I use Hidden Power after Confuse Ray so I can place a Negative Status Effect with the confusion so they have a very low chance to get off clean. Then spam Shadow Sneak or switch out.