once again, Bernie is right!
it's VERY easy to over-react to these shots. What I usually do on the slow dribblers is drop my to my right knee while keeping the left one up. I keep my left leg straight, my stick flat on the ice, and move my glove over to cover the 5-hole - pretty much "The Hextall slide" w/o sliding. Its the same thing I do on long dump in shots. That way the whole ice is covered, and it's extremely easy to stop the puck dead w/o any rebounds.
the simple answer is- don't think too much on what you should be doing and just stop the damn puck. once you stop to analyze a slow situaiton, you're screwed. sometimes it's better just to react and stop the friggin' puck!
on a side note- I also coach a women's B-team with a lot of beginners. On occasion I'll suit up to help them with their shots. I find it amazing how many shots I let go in that are so incredibly SLOW! It's just that you're not used to slow timing- the same reason why a baseball will strike out on a slow change-up.