Best I’ve been able to read on: Steaming can be better if all you’re doing is removing dust …and Soaking does more for the insulin resistant / ailing, etc. as it does remove more of the hay ‘benefit’ vs. just the dust. I’m only after managing the dust for cough/breathing concerns. I want all opinions: of what you use/how! I do not have a lot of hours in the barn. So, something more efficient even if an investment will be best for me. As well: while only 2.5 horses ( 
one mini) — the farmette is very small with very little / hard to keep grass, so haying is year round, in stall and out. so, it would be in constant year round use. I use Hay hoops in stalls, so I need something that I can ‘fill’ into those from vs. steaming or soaking in hay bags. In turnout, I could use an already drained soaker bin idea, or just toss the already soaked or steamed flakes. GRRRRRRRRRRRRRRR at the hay getting powdery on me. 
Very expensive 2nd cutting orchard (nice hay) bought, delivered, and stacked in Sept. in my VERY vented nice hay storage with ample air space above, and surrounding with huge ‘aisle’ between 2 stacked areas. Only 200 bales. Should not be happening.
I soak to remove sugars, have fat WBs and a fat Lusitano, a mare who foundered and a PSSM horse. I’ve coveted the hay steamers but they are so pricey and really I don’t need it. All of my horses get soaked hay (5).
My horse began coughing on a trip last Summer. The trailer had hay nets and the stall had wall feeders. So the horse had his nose in the hay for several days unlike conditions at home.
I was concerned about hay mold spore so…
I made a home brew hay steamer. Very similar to this http://www.horseandman.com/tag/make-…n-hay-steamer/ I used a metal grid to hold the hay from the bottom and just fed the steam from the hose end into the space. It worked well, and the horse liked the steamed hay over the non-steamed. Takes about an hour to steam a half bale (size of my container)
But …
Feeding on the open ground, avoiding wall feeders and hay nets resolved the coughing. The same hay was used.
