30' Pontoon trailer brake help?

[cleansquare]

Anyone know anything about trailer brakes? These are not connected to any sort of brake system in my truck...

Says hydraulic brakes and has some sort of actuator...are they activated by movement? When I take off or stop you can feel slack in the hitch like a couple inches. It has spots to grease by the hitch area.

I checked the brake fluid today first time in 3 years and it was dry but didn't take much to fill up.

I looked under the boat and the lines seem to go to only the front axle. There are bleeders on those wheels but how to heck do you bleed something you cant apply pressure to? Gravity bleed?

Also, there is a line that goes to nothing and I figured it was a vent line but its wet with brake fluid at the tip.

The boat



Some pics of the brakes