Properly export blender scene with materials format to three.js scene Completely beginner in blender and 3d graphics in general here.

My goal is to export a blender scene with models and materials (including textures) and import back in three.js scene.

According to here it seems I should use use the KhronosGroup glTF exporter for Blender (the json exporter for Blender seems to be removed). If I got it correctly the only materials that can be exported in glTF format are glTF Metallic Roughness and glTF Specular Glossiness (all the other materials are ignored during export). 
Thus here is the question: if the Blender scene use other materials like Principled BSDF or other ones, how should I convert them to use the Metallic Roughness or Specular Glossiness to get a result like the originals?

I've tried to do it manually, connecting for example diffuse or normal textures to the respective input in the Metallic Roughness but I got poor results. 

Any guideline on how to do this correctly would be appreciated (or any resource which explain how to do it).
As of October 2018, glTF 2.0 supports three material types: metal/rough PBR, spec/gloss PBR, and unlit/shadeless.

We are working on adding support for the Principled BSDF node to the Khronos Group Blender exporter. That work is in progress, and happening in a new repository (https://github.com/KhronosGroup/glTF-Blender-IO) which includes both an importer and an exporter. I'd recommend trying that for now. Note that some inputs to the Principled BSDF node (like anisotropy) are not currently part of glTF's metal/rough PBR definition, and will be ignored.

Other material types may be more or less difficult to convert into one of the supported glTF materials.