It's like a sport. If you don't work on your game, then you will never improve. I'm with you. Elbow's appraoch is just one approach. I see many opportunities for writng other than freewritng.
Opportunities exist for all kinds of purposes and audiences.
So far, I have not observed any time at all where writing actually took place. The classes have been mostly talk, talk, talk about writing, and virtually all of it has been by the teachers. Freewriting, journals may just work for you and your students.