I guess grass applicator preference can be likened to wire stripper choices. Everyone has their favorite. 
I wanted to see what I could do with the fly-swatter option before investing a larger amount of cash toward the project.
IMG_7814 by Edmund, on Flickr
For MY needs the $5. total investment really paid off. (I'll try to get a photo of the one I built but it really doesn't look all that fancy). A closeout store had the swatters at 3/$10 and the strainer was another dollar. Add another buck for batteries (some of the older ones used 9V but these have two AAs and seem to work just fine).
IMG_7802_fix by Edmund, on Flickr
This last scene is still being worked on, but the basic layer of static grass is in place:
IMG_7113 by Edmund, on Flickr
I make a few passes over the area with the empty strainer screen once the grass is in place. It gives it another chance to "stand-up and be recognized?.
Also, don't go too heavy on the amount of fiber you put down. It's easy to put down too much.
Another part of the technique is to allow the glue or paint to set a bit after using the static applicator then carefully passing a vacuum hose over the area which gets more of the grass standing and thins out the un-stuck fibers.
I have to chuckle a bit every time I think about doing the grass. It seems like I invariably get the screen too close to the metal push-pin I use as a ground.
POW! Scares me every time and the grass goes flying.
One more thing I'll point out that doesn't seem to get mentioned often...
REMOVE your DCC equipped locomotives from the area!
Fortunately, I thought about this before I began my grass-work. I did accidentally hit the rail once or twice! Might have a hard time getting warranty coverage on a decoder that saw 50 Kv!
There is a BIG variety in the colors and types of static grass available, too. This has more affect, IMHO, in the final look of your "field" than the applicator.
[edit] One more comment I'll make if you decide to make your own, try to find the most flexible length of finely stranded wire you can for the ground wire. A stiff wire can be a pain around some scenery details.
There are rubberized wires used for test leads or good quality volt meters. Try to find some of that.
Cheers! Ed