I like Buck's "bulldozer" idea, might have to try it sometime.
I usually just use the prunings to fill in bare areas, and pruning the plants seems to make them branch out better.
I just planted about 20 stems of rotala about a week ago, they'd been in the store long enough to develop roots on each stem, just plugged them into the substrate and I've got about 4 inches of growth, I'll be pruning them sometime next week at which point I'll use the trimmings to fill in the patch.
Usually with stem plants, I like to let them float for a few days before I plant them, sometimes longer. I've had a lot better results getting them to root that way. Lead weights get tossed immediately, all I get from them is a bunch of floating plants and broken rotted stems wrapped in lead at the bottom.