Unfolded and Laid Out UV Shells
My method of unwrapping UV Shells is to delete the default UV Shell and create a Camera Based UV Shell. This tends to give me a much bigger and clearer UV Shell to unwrap. The main tool I use to unwrap UV's is the 3D Cut and Sew UV Tool because it is very simple and easy to use. I cut seams where I think I'll get the best texture resolution and the UV Tool allows me to edge loop cuts by holding down the Tab button on the keyboard. After successfully cutting a suitable shell I Unfold the click Layout so that the UV Shells share the same UV Space
Applying Substance Textures
To start with I used the Steel Painted Rough Damaged Smart Material as the base texture for the helmet.
I used the Steel Scratched Smart Material for texturing the horn ornaments.
For the helmet plume I used Steel Medieval Stylized Smart Material to texture.
All applied textures together ready for rendering.
Substance Painter: IRay Render