Electric brakes present a purely inductive load. The EoH is different.
First you need to send a signal for the pump to turn on. Then you send a second signal to the proportioning valve. With light braking, it opens all the way and allows most of the pump output to bleed off, giving you little braking. The more signal you send, the less you allow to bypass and the more of the pump output that goes to the brakes.
Be careful not to cross the wires. You'll get working brakes, but they'll either do little or when they do engage, they grab hard.
The Prodigy- as I'm sure other EoH controllers do, has several adjustments that make braking much more smooth. First, you can proportion voltage to match the load and the trailer's braking capability. Second, you can adjust the pre-braking- when you first send the controller the braking signal, it pre-starts the pump and gives a bit of advanced brake signal to the braking unit. It eliminates that lag between truck braking and trailer braking.
be careful not to over-brake on the trailer. If it's doing the job of the truck and its own, you'll cook the brakes. I just saw one where it boiled the grease out of the spindles and welded the hubs on.