We've had 3-4 horse on our 5 acre property for the last 20 years, and have composted and spread their manure on our lawn.
My first thought is that there is nothing dry or dusty about composted horse manure. Taken from the pile, except for the very top "crust" the manure is damp - not dry or dusty at all.
For the first 10+ years I hauled the manure from the compost pile to the lawn using a small lawn cart trailer and spread it by hand. Eventually my back got tired of that and I moved to my JD 3320 tractor with a front end loader and a mid-sized ground-driven Frontier manure spreader - which appears to be a re-branded H&S manure spreader. We paid $2800 for it in 2006 when I bought the JD 3320.
Loading the spreader with the same tractor that pulls it took a bit to figure out. Now we use a 3PH trailer receiver hitch (
Flexpoint 3-Pt. Hitch Adapter Category 1 and 2, Model# FPHS-1 | 3-Point Hitch Adapters| Northern Tool + Equipment ) with a ball-less receiver hitch to connect to the spreader's split pin hitch. That allows me to fill the spreader without the tractor attached, then I back up to the spreader align the tractor hitch with hitch on the spreader. My wife usually helps me align the pin hole and inserts the pin. I lift the tongue a bit with the 3PH, she cranks up the trailer jack, and off I go ready to spread.
The ground-drive works great, though I have to think ahead giving me enough room to turn around - it doesn't like to be backed up, and to be careful not to turn into trees and fences (the tracker+manure spread is very long).
Once empty I turn off the beater mechanism and head back to the manure pile. I back up to the pile, my wife lowers the trailer jack, chocks the wheels, I lower the 3PH until it touches ground, my wife removes the hitch pin, and I pull away and use the FEL to load the spreader again.
One thing I can tell you is that I wouldn't want our spreader to be any smaller, since a smaller spreader means more trips and more hooking and unhooking. Our Frontier MS1105's box is 36"x97" with a 35 cubic foot capacity. We're not supposed to fill it past level, but we often do to minimize trips.
Oh, since we're spreading on our lawn we don't want the giant clumps. After spreading if there are huge clumps - which doesn't happen too often - we just walk the area with rubber boots and kick now the clumps. We wait a few days for the manure to dry, and then we mow the lawn. For the most part this gets rid of any visible clumps. Actually the biggest bits are usually root clumps from weeds that sometimes grow on the top of the manure pile. These simply get mowed down later.
I won't say we have a Better Homes & Gardens lawn, but I feel a lot better having saved, composted, and spread the manure on our property. Our neighbor dumps her manure in a garbage bin and its hauled off to the local landfill. Its hard for me to believe that's even legal, but apparently it is - as biological material - as opposed to being lawn waste.
Well, that's my experience. Good luck spreading!!