Mix 10 ounces of Dawn dish detergent with 2.5 gallons of water. For smaller applications, mix 2 tablespoons of detergent with 1 gallon of water.
Pour the mixture into the spray bottle or garden sprayer tank. Set the bottle sprayer to the "mist" setting. Pump the handle on the garden sprayer until the unit is pressurized. Check the garden sprayer setting by briefly spraying some of the mixture on a safe surface, such as the driveway. The spray should function smoothly with no leaks. Adjust the nozzle to produce a broad cone of the detergent mixture.
Use the spray bottle to mist smaller patches of moss or treat larger patches with the garden sprayer. Drench the moss thoroughly but be careful not to spray adjoining plants or grass.
Reapply the detergent mixture daily, if needed, until the moss turns brown and dies.
Use the rake to scrape and gather the dead moss. Dispose of the dead material away from the garden to eliminate any viable spores that may remain.
Monitor the area and re-treat if new plants sprout.