Image: Gep Pascual
... but don't do much of any sort of writing on a reasonably regular basis yourself (and school reports and comments on students' essays can't really count here), I figure you have basically two options -- not at all mutually exclusive -- to redress this potentially distressing situation:
1. Get to it, start writing regularly and make sure you experience at least as many writing genres and outcomes (and word counts) as you expect your students to tackle;
2. Be willing to negotiate the writing curriculum with your learners, at every stage and every layer.
I'm not going to feel comfortable or committed to learning something like automotive skills from someone who has never actually fixed a car (or only fixed one decades ago as a contrived demonstration activity) and figures, on account of his/her shinier and more spectacularly emblazoned overalls, that I have no right to venture some opinions of my own about what may or may not need to happen under the bonnet.
(Ouch! Twisted my bloody ankle getting down off my soapbox!)