Obviously, the fastest and easiest way is to use a power shredder. It'll make short work of as much dry ornamental grass as you can feed it.

The downside is chopped up ornamental grass foliage is very light and tends to blow away in the most gentle winds. The stems of bloom stalks of grasses like Miscanthus, on the other hand, are heavier, and work well as mulch.

I cut my grasses down, and separate flower stems from foliage. I shred the foliage and it goes into my compost bins. I cut the stems into 1-2" lengths with plain old pruners, and use them as mulch in container plantings. It looks good and works well.

I start my late winter shrub pruning in another week or so, and by the time I'm ready to start on the grasses, my pruner muscles will be prepared for the work.

I also separate my ornamental grass leaves from stems. I put the leaves in a heavy black bak and sprinkle irganic bloid meal over them. When the bag is full, I add two gallins of water and seal the bag with a tie. By next spring it will be completely composted. I haven't tried mulching the stems yet but will try the method mentioned in the previous post.