It could work this way:
Create a blueprint class based on the character class and add your mannequin as the skeletal mesh.
Go into your skeleton and add sockets to all bones that want to be able to rotate.
Now add collision spheres or static meshes and attach them to your sockets.
After that you need to save every rotation value of your colliders in a variable that is written to your Animation Blueprint every tick. Make an Animation Blueprint, add a Variable for every bone in your Mannequin you want to manipulate in VR and set them every tick in the Event graph.
Now you can use those rotational values in your Animgraph to drive the individual bones with a Transform Node, you can choose whether to add or to replace the existing values. Be aware that the initial bone rotations and axis vary throughout the skeleton, so make sure to have a proper look at those when setting this up.
All that is left now is to get the overlap events from your collision spheres/meshes when your VR hands intersect with them. While they overlap you can just add the local rotation of your hand/makes them snap to your hand rotation or whatever you deem fit.
This should allow you to pose the mannequin in forward kinematic fashion in realtime.