Use Reshade + SweetFX 2.0 http://reshade.me/
Copy the Preset text over the sweetfx_settings.txt file. Run Reshade.exe and point it at the game exe.
This Post Processing preset for IL2 Sturmovik is crafted to enhance the wonderful assets created by the developers and modders.
It aims to provide users with crisper, brighter, more colourful and vibrant graphics whilst simultaneously avoiding over exposure and over saturation.
I've tried to remain faithful to the palette the artists used.
It includes two PP antialiasing methods, FXAA and SMAA, both set to 'ultra' quality.
If running at 4k resolution then FXAA becomes unnecessary but SMAA could still be kept.
Remember to switch on FXAA in you GPU driver settings.
I've experimented with every resolution from 1080p upwards and my conclusion is that if you can run at 4k without ever dropping below 60fps then do and disable the AA in this preset.
Otherwise it best to use native resolution and the AA used here.
Forcing extra AA in drivers yields poor results with this title but the versions here work very well. Setting AF to x16 and Ambient Occlusion on won't hurt.
Don't bother with transparency supersampling, it does little and some reports suggest it worsens ground texture flicker, I noticed it at shorelines myself. Set Ambient Occlusion and Texture filtering to High Quality.
If it's oversaturated for your tastes then edit Tonemap - #define Saturation to a larger minus number.
If you feel it's over-exposed then edit #define Exposure to a lower value. You could also reduce #define BloomPower in Bloom settings.
Run Reshade.exe, navigate to IL2 exe, auto detection of graphics api will probably fail, manually select OpenGL. Be sure you are using OpenGL rendering and have edited your IL2 conf file for optimum quality.
Effect will load with game, toggle on and off with Scroll Lock key.