I've found that's the best way for me too. I rake my hands thru the clumps and the leaves just come out easily.
One year, my sheep got out and started eating my irises...it was very late in the year so I figured I'd just let him. That's when I realized that he was grabbing and pulling the limp old iris leaves off the roots and when he was done it looked great! The iris grew back better than ever. So now that's how I do it...I don't cut the leaves off, I pull them. You have to be careful not to yank too hard and pull out the iris roots, but it works really well when the leaves are very old and yellowing.