This might be misleading.

Open market operations (where the Federal Reserve directly buys and sells securities) are the primary means of monetary policy. Borrowing directly from the Fed leads to increased regulatory attention and public skepticism, and so banks avoid doing so except in emergencies. (The discount rate is higher than the rate at which banks lend to each other: If they won't lend to you then something is wrong). This means the discount rate is relatively unimportant in interest rate targeting outside of emergencies. I don't understand reserve requirements, but I'm told it's seen as a fickle way of influencing rates. So buying and selling bonds by the Federal Reserve isn't the last resort, but rather the favored means of influencing interest rates.