Is It Possible to Teach a Baby Sign Language With Only 2 Days of Time a Week?

Im an aunt and I want to teach my nephew sign language. He is turning 6 months soon and I think it's the best time. There's only one problem, I only get him on the weekends and I know that the people he live with are eather too busy or will refuse to further teach him themselves. Is it possible for him to still learn even though he only sees me 2 days a week?