Simply, the OBV is a remarkable technical indicator that can show us if the real money is really buying Bitcoin or quite the contrary they are selling. What we want to see when Bitcoin is failing to break above a resistance level or a swing high and the Ethereum already broke is for the OBV to not only increase in the direction of the trend, but to also move beyond the level it was when Bitcoin was trading previously at this resistance level (see figure below). Here is how to identify the right swing to boost your profit.

The most important feature of futures is that you never have to sell bitcoin ever again. Seriously. Why would you sell into fiat when you are concerned about a possible price drop? If you want to short bitcoin, then with futures you can simply "sell" or "short" the derivatives contracts and earn more bitcoin when the price drops -- so that your fiat value is the same or more if you use leverage. Of course you can also buy the contracts and  multiply your bitcoin when the bitcoin price goes up! But think for a moment how important this tool is: earn more bitcoin when the bitcoin price drops, and you effectively do NOT have to sell to fiat anymore. And with the power of margin leverage, you don't have to risk too much Bitcoin to take meaningful directional positions.
Upon a sale, exchange or other disposition of shares of a Fund, a shareholder will generally realize a taxable gain or loss depending upon his or her basis in the shares. A gain or loss will be treated as capital gain or loss if the shares are capital assets in the shareholder’s hands, and generally will be long-term or short-term capital gain or loss depending upon the shareholder’s holding period for the shares. Any loss realized on a sale, exchange or other disposition will be disallowed to the extent the shares disposed of are replaced (including through reinvestment of dividends) within a period of 61 days beginning 30 days before and ending 30 days after the shares are disposed of. In such a case, the basis of the shares acquired will be adjusted to reflect the disallowed loss. Any loss realized by a shareholder on the disposition of a Fund’s Shares held by the shareholder for six months or less will be treated for tax purposes as a long-term capital loss to the extent of any distributions of Capital Gain Dividends received or treated as having been received by the shareholder with respect to such shares.
•   Market Price Variance Risk — Fund shares are listed for trading on the [                    ] Exchange and can be bought and sold in the secondary market at market prices. The market price of shares will fluctuate in response to changes in the value of the Fund’s holdings, supply and demand for shares and other market factors. ProShare Advisors cannot predict whether shares will trade above, below or at a price equal to the value of the Fund’s holdings. Given the fact that shares can be created and redeemed in Creation Units, as defined below, ProShare Advisors believes that large discounts or premiums to the value of the Fund’s holdings should not be sustained. The Fund’s investment results are measured based upon the daily NAV of the Fund. Investors purchasing and selling shares in the secondary market may not experience investment results consistent with those experienced by Authorized Participants creating and redeeming directly with the Fund. To the extent that exchange specialists, market makers, Authorized Participants, or other participants are unavailable or unable to trade the Fund’s shares and/or create or redeem Creation Units, trading spreads and the resulting premium or discount on the Fund’s shares may widen and the Fund’s shares may possibly be subject to trading halts and/or delisting.
Since you bought 68.4246 BTC, you want to short 68 BTC and lock in the USD value. You will have 0.4246 BTC left over, which will give you a slightly long bias. You can either fix this by only buying 68 BTC in step 1 or by giving yourself more short exposure by shorting 69 BTC. Remember that CryptoFacilities contracts are inverse (which allow locking in USD) and are denominated in BTC