Hello, For more details please search Apan Vayu mudra in youtube n google and watch some videos to know the exact details since these mudras have multiple benefits for many ailments. However these mudras can be practiced between 8-15 mins everyday minimun and depending on the intensity of the ailment one can practice 45 mins daily in 3 sittings (15 mins per sitting).
You should practice it with two hands for max benefit but doing it with one hand also can help a little.