Volatility risk of MBS

As stated in VOL 4 P154. A portfolio manager can manage volatility risk by buying options or by hedging dynamically. The selection depends: 1. When implied VOL is high and the we expect the future realized VOL will be lower; then we hedge dynamically. 2. Otherwise we hedge by purchasing options. How to understand this? How to hedge dynamically?

Options have an implied vol in the premium price (Black Scholes). If you think the vol already priced into the option is too high, then you believe it is overpriced so go dynamic. If you think the vol priced in is correct or too low then buy the options.