Start 3ds max.
Load up your scene.
Enter the material editor.
Navigate to the material of your pit/startglow.
Click on it.
Right at the top you will see dropdown selection boxes for "Source Blend" and "Dest[ination] Blend".
Set one to Src Alpha and the other to Inv Src Alpha.
Repeat for all your glow materials.
Select all the objects that use said glow materials.
Click on the hammer icon in 3ds max.
Under Utilities (if set up properly), click on GMT Converter v2.52g.
Under GMT Output, make sure the output path is set to the folder you want to export into and click "Do Mesh"
Copy the generated .gmts to your ModDev path and fire up rF2 in dev mode.
Check the materials.
In case the glow appears inverted, re-set the Blend modes by switching them around (Inv Src Alpha for Source Blend, Src Alpha for Dest Blend) and re-export, copy over to ModDev, re-check.