Before I began texturing my models, I imported them to Unreal to be sure they worked. Majority of my models were fine in unreal, but for some reason the screws on the shelf I made would disappear and I had to adjust the model a few times to get them to work. The model of the screw on its own worked fine, but when combined with the shelf model, they had issues.

A lot of my models were made of metal, e.g. the stairs, shelf, and screw, so I textured them in substance with a metallic texture, then used a rough brush to add rust and dirt. (Below: shelf texturing process)

For the surgical tray, I got a texture of kitchen paper and added a blood splatter to it.

For the syringe, I textured the metallic parts in unreal and textured the green glowing goo inside it using nodes in unreal engine.