Midi controller via Teensy microcontroller

[audioguytodd]

Ok. So ive made a few MIDI devices with the Teensy microcontroller. (It's pretty damn easy actually). But here's my maybestupid question:

Say I want to do Transport. I can easily set my teensy code to habe the Play button send, say, a MIDI note on. And then go into reaper and have it learn that MIDI message for the play button.
My question is... How can I do this without MIDI learn?
I guess I'm asking what is the default data needed for that play button (or any other parameters like drop marker, etc.)

Is there a list anywhere?