Novation has published "Launchkey MK2 programmer's reference guide" with details about the protocol used for InControl communication.
Connect Control Surface plug-in (ACT MIDI, Generic Surface) to InControl MIDI input/output and send InControl initialization message (see the guide). For MK1 (older versions) use MIDI Channel 1.
 
You can then learn all controls normally. Advantages against normal midi mode: you can assign track changing buttons and use InControl switches. Note that InControl switches are also sending messages, do not use "Omni" input for MIDI tracks, select normal (MIDI) Launchkey input explicitly.