I would like to stress that washing all the soil off the plants with a strong force of water will really make dividing individual plants much easier. But, one added benefit is that if you wash the plants roots off really well, you can remove any nut grass, or other weeds that normally tag along with transplanted daylilies. Even then unless you are lucky, it is easy to send along aggressive weeds. I moved many daylilies from my parents yard and as careful as I was, still managed to import some mugwort. Thankfully, it was a bare minimal amount and it was never able to get a good start, once it does it is nearly impossible to get rid of.
