For what it is worth I use a an old John Deere, fertilizer spreader, (it looks like a drill box) (in the manual it had what was called grass seed cage) and since I could not find any new, I made my own and replaced the fertilizer agatator, (I think the fertilizer agitator would have worked OK, the bottom has slots that you open up more, on the JD spreader the cage is wheel driven direct, the cage is about 6" around and all it does is drag the seeds over the holes, (works well with the fluffy grass seeds),
http://www.tractorbynet.com/forums/projects/71609-lime-spreader-food-plots-4.html
in this post there is a picture of the seed atagator
very similar to a "Ezee Flow" spreader
similar to mine, (mine does not have the small seed boxes,)
I drag a single tree disk set very light behind it, (would like to find a old harrow the same width as the spreader),
here is a machine that looks interesting, (I would like the try the roller but not as aggressive), but most of my ground is blow sand,
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