As I promised a quick look at drum carding process for my sweater yarn on my Kitten drum carder. I flick carded and drum carded to get very clean smooth batts. The fleece was dirty and the flick carding helped remove the dirt and vegetable matter that didn't come out with washing.
Maggie Casey's Start Spinning book and video has good information about flick carding locks. A video here is good. Carol Rhoades has a free article on Spinning Daily here.
I took small bits of washed locks and carded both ends of the lock to open up the fiber and remove bits I didn't want. I like to flick card against my leg over a cut off bit of denim from an old pair of jeans. Then I collect the flick carded locks into a basket to box to card later. You can spin right away from flicked locks.
I've been saving the better flick carding waste to make some not so perfect batts at a later time.
I start by weighing out 15 grams of dark and light gray flick carded locks.
Then take a small bit of flick carded fiber.
Spread that bit out so it's very thin. So thin I can almost see through it.
I did two more rows of the same, overlapping just a bit as I go. Some carders don't have much of a tray so adjust as needed for your carder.
Then I crank the carder and it looks like the photo above. I started with the light gray then repeat the same steps with the dark gray then the light gray again.
Every so often I use my burnishing brush to smooth down the batt. I hold the brush in my left hand the way the picture shows and crank the carder to the right. I gently move the brush across the drum of the carder as I crank.
I'm only running the fiber though the carder once. The flick carding has opens the fiber up so well that's all this needs.