2500 RPM is too low... Like mentioned, go down at similar speeds that you went up at. Do not ride the brakes. Your major concern is to keep your breaks from overheating and you do that by NOT riding them on the way down.
Your computer should easily control the shifting going uphill.
You can downshift (going from say 5, down to 4) anytime you feel your speed is increasing too rapidly. Personally, I bake rather hard, release the brakes and see what gear I'm in. Press the down arrow or button once to go down a gear.
Your computer will not let you down shift if it would raise the engine above redline. Many people make the mistake of not letting their engine rev up... Anything not approaching redline is OK. It's made to run.
Just take it slow and you'll do great!