It will be a long haul, to be sure, if you want to sell the individual stamps as singles and get a decent return. The last 1286b that I can find sold on
ebay was over two months ago, in December, and the same seller has more of the same in stock that have been up on
ebay for sale continuously since at least last May. There appears to be very little demand at this price (50% of catalog). It will take some trial and error to find the right price point where singles and blocks will sell in a reasonable timeframe. Maybe a flurry of buyers will come your way at a $10 price point, or maybe not. There are only so many collectors that need a mint copy of this precanceled stamp. Most precancel collectors that I know are happy with a used copy that would cost a buck or less. If it were me, I would first try to sell the sheet intact, take the money and run. There may be a buyer out there after all. The fact that you found no full sheets at auction is not necessarily an indication that there is no demand.