NullDC with an iPac... some advice please. Thank you

[mike boss]

I got back to an old project today.
Long and short I can't really find any tutorials on this, so I'm hoping to find some help.
I have a MAME PC w/ iPac set up.
I've included some other emulators, most let me map the keys, NullDC will not allow the use of the MAME default key codes.
I'd like to avoid re-flashing the iPac.

So if I want to use the iPac as is in NullDC, can I just use some program where every game in NullDC will use the mapped keys ?

I'm not sure what to use, be it Joy2Key or Xpadder ? Any specific tutorials for using either with Null and an iPac ?

I found nothing on this specifically, I've never tried any of these programs prior, so I'm unsure of the difficulty level.

Thanks