The stain will come off with the proper oil for OP. The proper oils are nut or seed, untoasted, unrefined, cold or expeller pressed. Organic if you can get it.
Coconut oil will probably be your best bet right now if you can get your hands on it. I always found it had a super whitener effect. My first love is unrefined, untoasted sesame oil. Walnut oil is really good too.
Swish twice a day if you can (morning and just before dinner). Not too late at night because sometimes OP has been know to stimulate.
Proper OP will take that stain off and will start to really whiten your teeth beyond. I'd give it a few days to a couple of weeks to really start to notice. Yes, it can be very fast.