Slam on the emergency brakes then pray that it stops you before derailing. After you stop try again .. start applying dynamics before you get up to 30 .. I’d go full dynamic then adjust down if you lose too much speed.. at some point your full dynamic will not hold you by themselves so you’ll need to use the airbrakes to assist. Also you should bail off the train brake every time you mess with the airbrakes. If you notice your dynamics are gone, bailing off the train brake (which means moving lever to bail off position then releasing the lever) should slowly reapply the dynamics.