With both the hi and low poly meshes exploded(and uv mapped) I needed to add surface detail to the textures which I can now do through two methods.
The initial method I used for this was using zbrush to apply actual surface details to the hi poly mesh using alphas textures that modified the surface once it was subdivided to a high enough level.
The advantage to this method is you can have a lot of control over what you are doing if you know the tools well enough, you can customize and add extra details such as scratches to you mesh directly through zBrushes sculpting tools. However this method is very taxing on the computer and requires quite a bit of set up. My build required 7 subtools, each of which had to be exported separately and were prone to slowing down and occasionally crashing the software while building. This also means editing anything after exporting your mesh from zbrush becomes very difficult and, since I am still learning the workflow for making this kind of asset and am picking things up as I go along, this can cause me some severe problems if I encounter any errors.
However there is also another method I can use, one that is easier on my machine and simpler to work with the Quixel suite. Using Quixel, a addon to photoshop, instead of changing the mesh, I am instead skipping that and modifying the final textures on the low poly mesh directly. By making a colourID texture, a map of sorts to define what materials I want on my mesh and where through colours, I can simply choose from Quixels wide library of pre-made material types, and then apply them to all the textures types on my own mesh in that area.
Looking further there is even more that can be done with Quixels tools to make up for the lack of access to zBrushes sculpting tools if I wanted to add wear and tear to my models surface. While Quixel does have it’s own limits if you want any materials outside it’s library range, for the level I am currently at this would seem to be the best route for my to continue with for now, at least until I have learnt more about using zBrush and alpha tools.