I've never heard of using Jeyes fluid on lawns - as far as I know, its toxic to plants, and is of great use in unplanted ground which is to be left for months, or on pathways.

It's an old method of moss control. Best applied in the winter months, a 10% solution, used now you will burn the grass. I no longer use it for lawns. Best product is Lawn Feed, Weed and Moss killer.