Divide Asiatic Lilies in the fall
There is very little work to it and simply dividing and watering in this fall will result in more beauty for next summer.
Now that the leaves have yellowed, you can still see where they are. Grab a shovel and a bucket to hold the bulbs and go out there. Start in one section of the garden where the plants are still standing, working your way through the beds over a series of days if necessary.
Put the shovel in the ground a few inches out from the main stem so you get the bulbils still attached when you lift the dirt. Then, cut off the stem an inch above the soil.
Dump your dig onto newspaper and separate the mother bulb from the children. Do not compost any stems with fungus on them. Here's a how-to video from Ken at www.lilyflowerstore.com https://www.youtube.com/watch?v=GOLBduaaurg
You can replant all the children or only the largest ones. Last year I put the large ones in the ground in fresh soil and potted the little ones. Some grew into viable bulbs to plant out the ones that did not thrive went into bare spots to fend for themselves.
I also did what is called scaling lily bulbs. Here's how that's done - https://www.youtube.com/watch?v=-b7Oz9PWca8 from Nottingham Trent University. It worked REALLY well.