Power rakes, also called dethatchers, are push-behind machines that cut through thatch in lawns, such as dead crabgrass, loosen the thatch and bring all dead organic materials to the lawn's surface. Power rakes are extremely effective at helping to remove dead crabgrass from lawns. You can usually rent a power rake at your local garden or home-improvement store, instead of purchasing one. Using a power rake is as easy as operating a push mower, although removing dead crabgrass from you lawn does take a few extra steps.
Mow your lawn using the lowest blade setting. Rake and remove all the grass clippings.
Remove large patches of crabgrass by scraping the soil around and beneath the crabgrass using a straight-edge shovel. This will make the area of your lawn look patchy, but you don't have to remove the good grass along with the crabgrass.
Make one pass over the lawn area with the power rake. The power rake will cut grooves into the dead crabgrass and other thatch, loosening it and bringing it to the surface.
Rake away the dead crabgrass using a stiff-tined rake and dispose of the crabgrass in your compost bin or otherwise dispose of the thatch. Spread a one-half-inch layer of compost over the lawn area.
Spread a lawn starter fertilizer over the compost using a drop spreader. Then, fill the drop spreader with grass seed and make one pass over the area to dispense the seed. Be sure to choose grass seed that is the same or similar to your existing grass. Don't mix cool season grass with warm season grass.
Work the grass seed and starter fertilizer into the compost layer using the back of your regular rake. Water the lawn area just enough to moisten the compost, and then water lightly every day or twice per day when necessary until the grass begins to sprout.
Wait until the following spring to apply a pre-emergent crabgrass control chemical to the lawn area using a drop spreader. Use a pump sprayer to apply a post-emergent crabgrass control treatment if large areas of crabgrass return, or pull the crabgrass by hand if smaller patches appear.