Mow the lawn before scarifying. Set the scarifier so that the blades do not penetrate the soil too deeply but simply remove the top layer of lawn thatch. After scarifying, you can lime or fertilise if necessary. Where large gaps appear, you must re-sow in spring.
If you regard scarifying as too intensive for your lawn, you can also aerate it before winter. With aerating, steel springs comb the surface of the lawn without penetrating the soil too deeply. Unwanted moss and lawn thatch is thus removed. The lawn roots receive more air, water and nutrients again. In addition, the soil is slightly loosened, so that the grass roots can develop and spread better.