You don't need to raycast. If you set UICamera.genericEventListener to something, and on that something you have a script that has OnDrag function implemented, that function will be receiving a copy of all your drag events, letting you check what's underneath (UICamera.currentTouch.current).
There is no OnHover on touch-based devices.
You don't need to simulate anything in your case. Assuming you have a draggable panel, you can just give it some momentum (UIDraggablePanel.currentMomentum).