Well, in that case try playing the pentatonic scale and the modes using nothing but hammers and pulls. And play some string-crossing arpeggios using only hammers and pulls.

By the way, to keep the open strings from ringing out when you're doing the hammers and pulls, you'll want to cross your right hand over your left and lay your index finger across the strings right by the nut.

That'll get your left hand whipped into shape in no time. (Either that or you'll get really frustrated and trash your guitar.)