I built my static grass applicator, called a "Grassinator"from a post on the Z-Trains site in 2008. I can tell it's a good one, because I periodically give myself a nice little shock when I accidentally ground to myself.
I think the key to using one is keeping the area you're applying grass to very wet, so there is good conductivity everywhere. I just use the same isopropyl alcohol I use on all scenery applications, and there is enough water in it (especially if I use the 77% stuff) to keep good electrical conductivity.
This is particularly important if you're covering sparse and spotty areas.
When you're in town for the NNGC, I can show you my setup for it.