my method,
i took metal baking pans {2 for $1.00 at dollar general } and put holes in the bottom so the water can drain. filled them half full of potting soil . filled up with water and let them sit outside for about a hour to drain the water.
after draining i took about about ten cuttings from five different type crepe myrtle trees. each limb gave me three to four cuttings . i removed all the leaves up to the last two . scraped the bottom of the limb about a half inch to light green color showed. dipped in rooting hormone and pushed down into the soil almost to the bottom.
i took two metal rods that people use to hold installation under houses, get a small pack at lowes.
next i took a white 13 gallon garbage bag and sled the pan in with the rods on each side to hold the bag off the cuttings . using the ties to close the bag. now that the cocoon is all in place i placed it in a shaded area on my side porch , but make sure that the sun will not hit it . let it sit for 4 to 5 weeks , opening it every 5 to 7 days letting fresh air in. the water droplets will keep it moist . starting the sixth week open the end and let it air, do not close the bag anymore. every two days roll the bag back a little. by the 7th day remove the bag and spray with water to keep moist.
i used foam cups on some , trying different things and later started some red in flower pots and clear plastic bottles .