Most of the systems seem similar: blue barrel, timer gadget, hoses with brass nozzles run to stalls.
The thing about our system we love is not the equipment, but the reliable and knowledgeable guy who services it. Not sure how easy it would be to buy your own fly potion (are the chemicals controlled or tracked with paperwork?) but we have our guy who fills up the tanks and checks the entire system each time he comes out.
He also adjusts the frequency and duration of the spray cycles throughout the year when he comes. Very good service from someone who knows the system and is knowledgeable about the chemicals too.
Our several systems work quite well- it certainly helps!- but close neighbors who don’t have fly systems, assorted fans that create drafts that mess with the spray, and having a fair number horses in mare motel type accommodations all affect the end result.
We do have the system in the mare motel setups as well as the box stalls, but more of the spray blows around in the breezes.
At max cycles (8 times per day for I think 15 seconds per spray) it costs us about $20/horse per month for the spray. I think it is worth it, and the boarders know that we are making every effort to keep their horses comfortable.