There are a few things that it could be. The first is the brake shoes. Most e-brakes use a drum-in-hat type rotor in the rear, and there are shoes inside...
Villagers will sometime trade for string. Witches have a chance to drop string upon death. Steal string from other players. Use Creative Mode/Commands.
With angle parking, you want to make sure that you pull away from the spot at an angle where you're giving yourself enough room to adjust as you back up....