1. Use the .blender file [spoiler]on the discord[/spoiler] with the UE4 Mannequin Skeleton ready. The mannequin skeleton was imported with primary -X and secondary +Y axes. Try to ignore the shitty skeleton, Tim Sweeney's ways are weird

2. In the same blender file, import the fbx of the character you want to import into UE4

3. Scale the mesh of the character to better match the a-pose of the grayman mannequin
4. Remove the character's armature so all you have is a mesh

5. Follow the tranny guide attached to parent the mesh to the root of the mannequin and then rig it to the UE4 skeleton

Tranny Guide courtesy of Tippy

7. When exporting as an fbx, make sure in the armature option that primary -x and secondary +y are selected

8. Your character should now be UE4 ready and ready to be given to a map maker
(fuck optimization lol)

remember that there's a chance someone else can download it
so don't use a character you would be upset if you saw used elsewhere or by someone else