AnKor's February 2017 shaders added another way to do this.
For the cockpit or gauge texture you can create a dds file with the proper suffix to define it's behavior.
Available codes area:
+lrgb => colored light map, rgb channels.
+lr, +lg, +lb, +la => grayscale light map (i.e. just the brightness) in one of the channels, i.e. "+lr" is light map in red channel.
+sr, +sg, +sb, +sa => specular map in one of the channels.
+gr, +gg, +gb, +ga => glossiness map in one of the channels (black - "rough" surface, white - extremely sharp highlights)
So, if you want to have both specular and glossiness maps you need to name your texture like this: main_texture_name.+sr+gg.dds
This will tell the shaders to look for specular map in red channel and for glossiness map in green channel.
For some odd reason the previous implementation of self-illumination textures (+lrgb) worked as if the original texture was lit by external light source instead of actually emitting the light.
This means that if you had absolutely black original texture, then no matter how bright the lightmap is you would still get the black color as a result.
To fix it AnKor introduced a new suffix for textures: +light
These will actually add the lightmap on top of original texture, so even black surfaces will appear "emitting" the light (think windows in buildings that look black during the day being lit at night).
In addition to the ones listed above there are now two new suffixes for such emitting textures:
+nlight -- these are only active at night
+clight -- these are for cockpit use and only active when cockpit light is switched on
Keep in mind that only ONE additional texture of this kind can be used, i.e. you can't specify +light and +nlight for the same original texture.
Using the P-61 cockpit light effect as a starting point:
In the TextureMagic.ini there is an entry to define the Cockpit light and you can set that to look like the dim UV black-light sheen if you want.
light_uv.dds=Spot|130026|2.0||||30|30
In effects.xml you'll need to add (you'll also need to create a light_uv.DDS file):
<cockpit_light_uv ClassName="Shockwave" PullOnGround="0" CountCycles="1" Pulse="0" InitialDelay="0" Duration="99999" FadeInTime="0" FadeOutTime="0" Pause="0" PosX="0" PosY="0" PosZ="0" InitialSize="0.0001" FinalSize="0.0001" Texture="light_uv.DDS" BlendMode="QuadSprite"/>
In the aircraft xpd you'll need something like: (the position will need adjustement for each specific cockpit other than the P-61 in this example)
<Effect Type="Track" EffectName="cockpit_light_uv" PosX="-0.475" PosZ="3.3" PosY="0.375" Pitch="110" Heading="20" MinVel="-999999" MaxVel="999999"/>
<Effect Type="Track" EffectName="cockpit_light_uv" PosX="0.475" PosZ="3.3" PosY="0.375" Pitch="110" Heading="-20" MinVel="-999999" MaxVel="999999"/>
In the SJT+P61_shared_textures\VC_texture_files you can rename the files to switch on with the cockpit light. For example:
a_gauges_1_no_alpha.+lrgb.dds becomes
a_gauges_1_no_alpha.+clight.dds, but I also had to boost the green channel at least 50% to get the phosphor/radium glow look.
The only unintended side effect I noticed was that the gear lock indicator lights still change colors, but only light up brightly when the cockpit light is turned on.