I'd also suggest you look to use a selective ( ie broad leaf) weed killer before hand. Also it really pays to aerate your lawn with a fork to a depth of 100mm. Then why not go the extra mile and spread a little of top dressing with a some grass seed to brush into the fork holes.
Do all these things and your lawn will improve dramatically. Scarifying alone is not a miracle cure-just one part of a range of measures.
Edited 1 time(s). Last edit was april 21, 10:14am by tomdhu.