This is not entirely true. All you need to do is make a change to the
FSUIPC4.ini file in the General section.
Find the entry "ShortAircraftNames=False" and change that to "True".
Now, those Aircraft specific entries can use a subset of the aircraft
"Title=" entry as it appears in the aircraft.cfg file for a given aircraft.
The "Title=" entry for most paints, if they follow the default
convention, will \begin with the base name of the aircraft followed
by some verbiage identifying the paint....B737-400 Paint 1,
B737-400 United, B737-400 Air Canada, etc.
With the ShortAircraftNames set to True, the FSUIPC4.ini file aircraft specific entries can be [Buttons.B737-400] or [Axis.B737] then those settings will apply to ALL paints of that aircraft.
There is also another feature available ion FSUIPC4 that allows you
to set "profiles" to accomplish this task. I've not used that feature
since I have been using the short names approach since day 1. I find
that it does everything I need when it comes to making control
assignments/mappings for all my aircraft.
The documentation included with FSUIPC4 is quite extensive.
I suggest you bookmark the location for the Advanced Users Guide
PDF file as it will answer most of your questions, as well as
generate a whole slew of new ones
Paul