I used to double-dig, but do so no longer; just too daunting, really, and I have come up with other methods to work from the top down. I think your soil sounds like it needs more than the cardboard method in the link below, but how about this: What if you roughly prep now, so that winter can do some of the work for you? With each heave and thaw cycle of the coming winter, some of the amendments you pile on now will start to work their way in. I’d break the ground (tiller or spade and spading fork) and just leave it opened up, again roughly…not all perfect by any means…and layer on a lot of sweet peat and fork some of it in once. Then forget it till spring, when you can work it again and load in lots more compost. There are some basics in this other Forum thread that would be work browsing through, as well, on mulch and compost and so forth.