Last year I offered to mow the lawn (about 50 square metres) of an elderly friend. However, I found myself mowing moss rather than grass. I would like to change this moss lawn into a grass one, but my friend does not want to have to put up with going through a stage of having a lawn of blackened killed moss. Nor does he want to remove the surface and start from scratch. Is there a way of making the change gradually while still maintaining the nice green appearance the moss currently gives? Cost would have to be minimal.