This used to be me. I now realize that the reason for my grogginess was that I was totally dehydrated after my 10+ hr sleeping marathon. I now sleep with a water bottle and try to drink half of it before going to bed. When I do this I find that I will naturally wake up after about 8.5 hrs, drink the remaining half of the bottle, fall back asleep for 30 min, and then wake up feeling great. Wonder if this could work for you too