Hello. You can use Anutaila available at Ayurveda stores for nasal instillation. Doing this will reduce greying of hair. Instill 2 drops of Anutaila into each nostrils 2 to 3 times a day. This is called Pratimarsha Nasya.
Once the white hair conversion starts it is very difficult to control it. Usually no applications or oral medicines work rather they may/ may not help. But what can definitely help is modifying your lifestyle. Eat healthy (no junk food ), sleep on time (11 p.m. latest), wake up by 6 a.m. and go exercise. This helps is reducing the oxidative stresses in the body which trigger whitening of hair. For treatment, you need to visit a dermatologist. You will only waste time trying to use oils and lotions and shampoos 'suggested' to you.