Your problem isn’t Unreal4, as you mentioned you used Unity before and just put a normal map and a diffuse in the standard shader. You need to learn how the different textures work in a shader/any game engine. Wetness reflects, looks shiny, so it for sure needs a specular texture. Combine it with a roughness texture. I understand why you don’t know about this, the Unity engine doesn’t allow you to create custom materials easily, you gotta run with the U5 shader or start learning how to code shaders. In UE4 just create a new material and experiment with the textures, you also have many content examples that can help you creating the look you are trying to get.