More specifically when it will be warm enough to open the doors & windows for ventilation in part. Though I certain you already know that part. But I am laying odds you may have to do a tear down of the lathe and paint it piece meal to get it right the first time. And that I lay odds is something you are not all that thrilled about. Because of the time you will not have the lathe available to you.
But then there is the question, do you need to repaint then entire lathe? Or just the parts that will getting exposure to the coolant?