deleting post. its kinda outdated and very old post.
I don’t know much about importing from 3D softwares but I do know that this goes in #help-and-feedback:game-design-support
Animation can be done by Welding the Handle of the Tool to Players Hand. You dont need to do it in runtime.
Take a Dummy Character (or make one using robloxs creator)
Position the tool in Workspace. And alas add a weld constraint and set Part1, Part0.
Now go to Animation Editor or any other plugin which helps animate and you can now animate the hands the way you wish.
TIP: After Animation is completed. Update the Tool Grip to be set to the First Frame of Animation.Else the tool can be in wrong orientation/position.(U Can Use Tool Grip Editor Plugin for this.)
About Hitbox. You Just take a Part or Mesh that Approximately Covers the Mesh.
Now position it and Add a Weld Constraint to it. Set Part1 and Part0. Set Transparency to 1. Set Collision Fidelity to Precise if it isnt ( for meshes only ).
It is mostly done using Bone Constraints. I am not aware of how it works. But i am aware of a plugin that helps achieve the same. I will add the Link in Edit.
EDIT: Link:-
https://www.roblox.com/library/2908380847/Rig-Editor
Also great weapons Btw. Try using more effects/Particles.