The basic structure of the LIRC file you want would be the same as this one for NEC1 device 4
[Link: lirc.sourceforge.net]

Function 8 in the backwards hex used by LIRC is
20DF10EF

The 20DF in each function is the backwards hex for the custom code for the device number 4.

The 10 above is backwards hex for 8.

The last two digits (EF) must always be chosen so those two plus the function add up to FF. 10 hex plus EF hex equals FF hex.