Well you can simply mow the entire carpet down with a pair of scissors, new leaves will grow from the roots and runners left under the substrate. I do this as the carpet of glosso is growing in but at some point I usually pull the entire carpet up and just replant a couple of runners and let it all start again from the scratch. You can also just pull out many runners leaving a thinner layer, it will quickly fill in the gaps again.
another thing I have heard...get a razor blade and cut out 1"x1" or so sections....remove that glosso and let the neighboring glosso re-fill.. ..just keep that up. I will eventually have to try that method....as opposed to gutting and replanting each time