There are actually a few methods to create your panels:
Paper panels
Engraved panels
Screen panels
Professional panels
DIY panels
I'm sure there are more methods, but these are the main ones.
Paper panels
Now, these panels aren't realy made from paper. I just like to call it paper panels, because you use some paper... This is one of the cheapest methods for backlightable panels. Basicly, what you do is print out 2 drawings. 1 colored and 1 black. You take a sheet of plastic, Lexaan for example (polycarbonate), and you put the colored paper behind. This way, you get to see all the gauges, text, knobs ... Then, you take the black paper (printed on transparant sheets), and put it behind the colored one, to block the light. There's a small difference in design between the colored ones, and the black. On the colored ones, everything looks like in the cockpit you want. But on the black ones, everything is black, except for the parts where the light has to come trough.
Engraved panels
This is probably the moste exspensive method, but also the most realistic and durable. You take a sheet of Lexaan or Plexiglass or some other plastic, paint it the color of you panels, and then engrave where the light has to come trough. To get the white look, you can paint the back white, or use white plastic. Make sure if you use white paint that the light can get trough! You can do it this way if you have a steady hand, a CNC mill, or a laser that can do this. Or you can search for a company that does this for you. Be sure your budget allows this!
Screen panels
This is the easiest method. You take a screen, put the right panel in your simulator-game on it, and you're ready! Altough this is less realistic!
Professional panels
The last method is to buy your panels. You can either buy panels from an old cockpit, or you can buy new ones from company's like
http://www.flightdecksolutions.com
http://www.engravity.nl "Engravity panels" (note: they are not to scale!)
(add to this list!)
DIY panels
This method isn't backlightable, but still very good: DIY Panels
non-reflective panels TIP
A very interesting idea of how to make panels anti-reflective is presented in this thread from Frugal's Forums: http://forums.frugalsworld.com/vbb/showthread.php?t=79135
Quoting "Marv":
"Try a hobby store and find a can of "Dull Coat" clear spray paint. There are also dull coat spray paints used for photography. They work well. If you have an air brush, you can mix a clear coat with a little talcom powder to get a dull finish."