to short the dollar, all you have to do is borrow dollars and use them to buy something else that you expect to go up quicker than the balance of your loan due to interest.

trading bitcoin with leverage is shorting the dollar.

what saylor is doing is shorting the dollar.

in fact, just buying something with dollars at all is shorting the dollar, even if you have no intention of selling it for dollars later. that is equivalent to just never closing your short position.

buying a house is shorting the dollar.