The above advice but also get your weight off the seat (if you are coasting).
With your weight off the seat, your legs will be able to quickly act as shock absorbers.
You'll be able to stop/slow-down better if you can move your butt behind your seat. Practice (get used to) doing this on a normal (flat ride).
Also, try to take the lane rather than riding close to the right side of the lane. You'll have more space to maneuver and more options to avoid rough spots. Doing that entails checking traffic before the decent and takes some practice and experience.
Last edited by njkayaker; 07-23-20 at 10:22 PM.