I want to export a PBR asset from Blender to UE4, but for the metallic parts I obviously need the specularity or metallic maps which are not in baking options of cycles. I've seen people talking about using emission or using Blender Internal and 'draw' it manually, also generating it with painting software because its just a black and white scale I think. I can't find a clear answer to this or a proper way to proceed.
Thanks and sorry for my bad english.
Also, the object has different metallic materials, how should I integrate them into 1 and only map? Thanks