and most CW users use either Rod & Staff or Harvey's Elem. Grammar. CW sells a Harveys workbook, and the lessons are scheduled out for you in their Instructor's Guides.
If you use R&S, which is what I do, you can just work through the book, skipping all writing lessons/chapters, or you can work on the skills suggested in the CW manual. For example, the Grammar assignment in the I.G. may be a chapter on "Sentence Making" in Harvey's. You could work instead on the Rod & Staff chapter on "Sentence Construction."
You'll be able to skip some exercises in R&S. I only schedule grammar one time per week, for 20-30 minutes when I'm doing a CW lesson. If we take a week off of CW, then we do more grammar. This has worked very well for us.
HTH,