After you’ve shampooed your hair, use Kerastase Elixir Ultime Oleo Complexe to get the most incredible shine. It is not greasy, and doesn’t weigh your hair down. Just use a tiny amount in your palm, rub together and work in. Keep using a tiny amount until you feel you’ve got enough.
It is somewhat pricey, so get the cheaper travel size on Amazon.
I think this is the best hair shiner, but I have fine, dry, over-processed, long straight hair. Everyone has a different hair type.