When you start your counter custody training, start slowly. First, learn how to escape from restraints, then get your tools and your restraints. Train with friends, and never restrain yourself when you are alone. Start with zip ties. They are the easiest to get out of. When you are proficient at escaping from zip ties, move up to rope (nylon and synthetic), and then to handcuffs. When you start working with handcuffs, start by using chain linked handcuffs and have your hands cuffed in front of your body. When you are good at that, have your training partner(s) blindfold you after they have cuffed your hands together in front of your body. It is a lot harder to unlock handcuffs when all you have to find the key hole is your tactile senses! When you are proficient at this, then start working with your hands cuffed behind your back. Switch to hinged handcuffs only when you are experienced and wanting a challenge.
By doing this kind of progressive training you will build up your confidence. If you start with hinged handcuffs behind your back, then you may be setting yourself up for failure, which can lead to disillusion and you giving up on training.