Hi,
I think what you want to do can be achieved without any problem. You mean the animation which you have is an animation of both hands attacking at the same time, right? If so, you can easily create alternating movements by first keying the pose using the hotkey Ctrl + Shift + L or the Key shown button on the Dopesheet view at the end of the attack, then selecting the keys for one arm and shifting the timing. Once you achieve the alternating movement, you can duplicate the keys so that each hand attacks twice, you will have the animation you are looking for.
If the Key shown button is new for you, please see this section of the user guide:
Keys - Spine User Guide: Key shown
To shift the timing of keys, you can use box selection:
Dopesheet view - Spine User Guide: Box selection
Sorry if this is not the information you are looking for. If you have any further questions, please don't hesitate to ask!
