Just run over it a couple of times with the mower. Generally speaking, "reel-mowers" are far superior to rotaries, as they give amuch better finish, and the "scissors action" of a reel-mower is much more healthy for the grass than the "chopping action" of a rotary.

However, in this case, there's a good argument for getting out your "backup" rotary, as it distrubutes the cuttings (and the DP) better - don't use the grass collector; use the "mulching" setting.

Unless it's the white variety!!