Hi. What is wrong with your grass apart from the moss? Is it long term pasture or re-seeded? Is it full of nettles and thistles? Is it undergrazed? If so, then topping will help, or cropping part of it as hay if it's that long. We usually top a bit later when the grass seed heads are trying to form; the purpose is to enable plenty of fresh growth and to prevent the plants from seeding (the new growth is more nutritious). Also by topping, stronger growing grasses are held back to let some of the tastier ones compete. We harrow when the grass is short to get out moss although it's not that effective. You could also roll it to smooth out lumps and bumps and mole hills, and to tiller the grass (bend it to make it produce more stems). Other things would depend on just what is wrong with it.