Asked on 15 Sep 2018
Shorting US market
Buy put options, or sell call options on the Etf. Both will achieve roughly the same effect though the obligations and funding amount will differ. Buying puts mean you need to pay to own the option contract, no margin required. If the price of the underlying Etf goes below your strike price, you can sell off the position for profits. Selling calls mean you will receive money to holding the position, though if the price of the underlying Etf rises above your strike price and the option gets exercised by the option buyer, your account will be holding x negative amount of shares, where x equals number of contracts sold times 100. You will need to put up margin with the broker to sell option contracts. One thing about selling calls is that if the Etf price does not go above your strike price upon expiry, the contract expire worthless and you keep the premiums you received. And you can repeat the process. I'm using thinkorswim to trade options and it's quite user friendly.
15 Sep 2018
Open a Forex brokerage account. There are Index futures that you can short. Capital required is lesser than shorting using CFD brokers.
You can try the following forex brokers: axitrader, IGmarkets, CMC markets.
No need any fancy options if you just want to have opposite exposure to the QQQ ETF that matchs NASDAQ 100 just get the ProShares inverse ETF (ticker PSQ) which is designed to give daily change same as QQQ but opposite direction.