Easiest way to do translate/rotate player's arm in third person

[poopoodice]

After researching what I'm trying to do now is hide the hand model in pre event, and after everything's being renderer, I make the arms model visible and trying to do some translation and rotation of it. Unfortunately it is not as easy as just

leftArm.showModel = true;
leftArm.render(matrix, event.getBuffers().getBuffer(model.getRenderType(player.getLocationSkin())), event.getLight(), OverlayTexture.NO_OVERLAY);

The rotation angles and position must be set before actual render the model, otherwise it will just be there, ignore player rotations, and... acting weird.

What do I actually need for this? Do I even need a custom PlayerRenderer and PlayerModel?