Problem with single twist in pattern

I have been following this free pattern for a single twist turban style headband, but I am having trouble with the twist itself. Here is a link to the pattern:
http://www.yarnspirations.com/pattern/knitting/twisted-sister

I have done cables before, but I am not sure what C18F means exactly. I assumed it meant slip 9 onto the cable needle and keep in front, K1 P1 the remaining stitches, then knit the stitches on the cable needle, but for some reason it does not come out looking right. Perhaps I am doing something wrong but the middle of the twist always ends up rather loose, disheveled, and nothing like the picture itself. Can someone help me out?

Nice looking headband. Yes, that’s the correct way to do the C18F (the held sts are also in k1p1 rib). It’s defined under the photo, after the description of version 2.
This large a cable isn’t easy to do because of the large number of sts. Have you continued to knit several rows after the twist so that you can see what it’ll look like? I try not to pull to tightly or leave the yarn too loose when knitting the first set of 9sts but probably too loose is better than struggling with too tight.
Can you show us a photo of what you’ve knit so far?

I was also going to suggest you knit further after the cable. It sometimes takes several rows to see what a pattern will look like.