Put on some cheaper, durable tires to practice braking techniques. I used Continental Ultra Sport II a few years ago after resuming riding a road bike because they're very durable and grippy but also pretty darned good tires for the money (used to be under $20 each, not sure about the current price). Great tire for an indoor trainer too, so I don't need to swap wheels on my old school steel bike to ride outdoors.
Some folks recommend sliding back on the saddle, or even off the rear of the saddle, for straight-line emergency braking -- such as on a downhill, or emergency stop to avoid being struck by a negligent driver. It's not the best technique for every situation, but you need to practice these techniques to develop the muscle memory, instinctive use and confidence.
On gravel and loose stuff some riders recommend staying seated to keep weight on the rear wheel, both for seated climbing and most braking. Some techniques include deliberately locking up the rear wheel to dig through gravel and loose topsoil to hit the firmer stuff underneath. Again, you have to practice to decide whether it works for you. Worth using some inexpensive but durable tires to practice.