Stephen Stewart wrote:

I had heard that scarifying helps spread the moss when it's alive so you're
better to wait until the mosskiller has had it's effect before scarifying.

I hope that's not true because I expended much effort on Saturday
scarified my extremely mossy back lawn on Saturday before mowing it. I
was intending to weed & feed it today, but didn't get round to it. So
much to do at this time of year!

Whether this is true or not I'm not sure but there's certainy no harm in
scarifying afterwards.

If nothing else, it's very good exercise.

Peter