Wiring gps stereo controls

[dsrtrat]

So i got a decent deal on an older Tsukayu gps fairing. It has an older 7" inch system. The newer thumb controllers do not work with them. So my queation is, how does one go about wiring up a thumb controller? There are two swc wires and an swc grnd. From what i am reading you can control it by hooking up buttons that create different resistance?

Anyone out there have any info?