Making a realistic character material and rendering questions

Hi all
I am just getting started with UE4 and I am currently browsing through the documents and watching related videos. Lots to absorb and I hope I can be pointed in the right direction here:

I am using realistic character content setup

  • I removed turned off all lights and cameras and made a simple spotlight and new camera
  • Connected the material and nodes used on the realisitc UE4 bust to my character bust

Questions:

  • I have an Xnormal Cavity map currently being used for Specular. I want to combine this with another Cavity map I created in Zbrush. How do I combine properly?

  • I am currently using a Bent Normal Map from Xnormal, what is the best practice for combining and masking another normal map to this one (I will be combining with a tileable tangent normal map with microdetailing?

  • Importing into UE4 is challenging. How do I import other assets for this bust so they snap in place on the bust? This bust is an FBX. I found bringing obj to the scene will not align with the bust.