If it's speed based, the Glameow should always be hit by the multi-target move first since it's got 40 speed and the Stunky has 36 speed. (All in-game Pokemon have Hardy nature and have 0 IVs in everything, with the exception of the all-flawless Battle Tower Pokemon. Or so says yamipoli.)
All-WHAT battle tower pokemon? Son of a BEACH BALL.
*edit* With a fast partner, surf hits the partner first. With a slow partner, surf hits the glameow first. I can't test messing with its speed, really, since string shot hits both enemies, but I'm guessing it does work with speed though.
UGH that's annoying. Still don't know the details about destiny bond/aftermath etc.