IMO the best way to direct your hits with PCI is through your swing timing - intentionally swinging early or late, that is. You can kind of influence it by hitting on a certain side of the PCI too, but that's more likely to lead to weaker/unpredictable contact.
A pitch on the side of the plate you want to hit the ball to is the easiest to direct, but if all you're looking for is an infield groundout to move a runner, as a lefty you can even try to pull a ball on the far side of the plate and you'll probably roll over on it, but still hit it to the right which might get the job done.
Contact swinging can be pretty useful in this situation too, since you're not necessarily looking to hit the ball hard. The swing timing window is larger on contact swings, meaning you can get away with swinging even earlier or later than normal, and still be able to put the bat on the ball.