I installed a new turf lawn a few months ago and, after letting it get established, used Evergreen on it to help it through the summer.
Evergreen is small grey foul-smelling pellets, 1-2 mm wide. The recommended 30g per square metre amounts to a palm-full of the stuff spread evenly over the lawn. It is easy enough to scatter by hand. The pellets are small enough to disappear down through the turf and to the ground, where it's needed. It requires no watering-in, so you don't need to wait for rain to use it.
I am no garden expert. I just want a decent-looking lawn. It certainly perked up my lawn very quickly, and seems to have helped a couple of thinner patches to recover a produce new growth.