Lot's of height from the bases is key, along with good control and a strong hollow body. The flyers want to make sure they're staying straight and not v-ing inward or arching back. For girls whom are comfortable but need cleaning up try the T-method. It sounds terrifying but is very affective for fixing body position. The flyer starts with arms in a strong T, when the bases pop her she must keep this position, hollowing out and staying straight. Her only job is a slight turn of the head and keeping this position; one of her bases will initiate the twist and when down properly she'll land in her v, coming all the way around. The following twist should be clean and beautiful and if the flyer doesn't do anything but stay tight it will got all the way around, maybe even 1 1/2. A lot of flyers think that in order to get around they need to completely yank there body, but in reality you don't have to do much, especially for a single. An experience flyer should be able to make a full circle will on a turn on her head and no other twisting from herself or her bases. A less scarier method, try having the flyers lay on the ground and have a base hold there feet up; they should still be hollow like a plank, hips coming off the ground. Have the base or flyer initiate the twist, cleanly fulling around once or twice. You may want the full to be done without the base as it can start to feel icky on your neck after awhile. For prep fulls, try v-arms and in the pop have the flyer hollow as if to cradle except instead of going straight down she'll bring on are straight down to her side (left), look left as well and cleanly/sharply bring her other arm across her body. This will create a clean twist with safe arms that aren't going to knock anyone in the face. You can choose whether or not to have the flyer catch herself but I've found that once they get this motion down, if you stay hollow you can double easily and with only a little extra pull.
There are about a thousand and one other tips and tricks, it really all depends on what works right for you and the kids you coach. If you have any more questions or need help with drills for singles or doubles just let me know. Good luck!
Just read you post one more time, here's a couple other things. For singles out of an arabesque make sure the flyer hits a solid T before twisting. You can either bring hands to sides or wrap them around the body. Just make sure elbows are in and that the flyer is waiting for the pop. Also, a video for kick singles.... Got this vid from @loverin46 .There's another video as well on the channel. So much help!
