Definitely possible, ladies do it for NFP and FAM all the time! You just treat the post partum time like one long pre-ovulatory phase.
You can skip the temps and follow a mucus only system of charting, like the
Billings Ovulation Method or the
Creighton Model. Following one of those will tell you everything you need to know about your fertility without the temps.
If you'd really like to include temperatures, you can learn about post partum charting here:
Postpartum Class