Hm. I was always able to hand express a *little* bit after pumping, even when I pumped myself "dry." In other words, I was usually able to get a few moderate streams which then quickly decreased till they were mere drops.
How much is your child drinking at each feeding while you're at work? (I take it she's consuming more than you're producing...).
If there's a lot left after the pumping ceases being useful, then perhaps you could just strip yourself out by hand. I take it, as well, that there's nothing wrong with your pump, and that you've recently replaced any parts that wear down (if any - I've not used the PIS)?