Dear @Shrinath, placing VK on forehead or crown with intention of serenity is enough to initiate restfulness and peace at mind. But you may practice Calm down serum if you want or energy of "Aum-Shanti" will do the same.
In this process, as you said, the third eye is covered, but here the Third eye (Ajna Chakra) is touched by the divine himself. @ Shivaprakkash is absolutely right when he says that he does not allow an alien-touch on his Ajna Chakra (Please read link of Energy Suckers). Since our Astral Chakras are the administrators of the rest of the body and related environment, it should be surrendered only to trusted authorities ie. Guru or the Divine.