I autorigged my mesh on Mixamo to enjoy quick skinning. I haven’t seen yet a better autoskin result from scripts.
I haven’t downloaded any of Mixamo animations though.
I just mapped their rig onto a CAT and then retargeted Third Person FBX animations from Parrish’s tutorial.
What I did was bring in Mixamo T Pose FBX to Max and run AUTOCat script from Mixamo on it.
If result includes a Morph target (used to position mesh somehow) then use Collapse To to dissolve it out (but keep Skin data obviously).
Note - There is a similar script from Mixamo for Maya, but I haven’t used that.
Once character is a CAT rig you can dispose of Mixamo rig.
If I have an existing FBX with animations (like ThirdPersonFBX ones in Parrish’s tutorial set on Third Person Character on Unreal Engine ), I use Sticky Lock by Luke Maskell (scriptspot.com) to match CAT bones to FBX bones. Scaling BaseNode of imported animation to match CAT rig may require some checking. It works pretty well and saves a lot of animating time if you’re just setting up a prototype with your own asset. You’d still want to animate custom animations later on.
To export from 3dsMax, select mesh and CAT rig, (not just mesh or you get a error on import into UE4).