Flat/Mat Paint

What would I have to change, so my paint has the flat/at effect?
Flight Simulator and other chat
https://forums.simviation.com/phpBB3/
https://forums.simviation.com/phpBB3/viewtopic.php?f=15&t=36025
P.S. Actually it's the intensity (darkness of grey) of the alpha channel which gives texture shine; conversely, a white alpha renders the least shine
I found out the hard way when i forgot to convert my normal bmp ro DXT3. The finish looked dull and flat, like in the older sims.