Studies have shown that people retain a very small percentage of lecture material. Just as a small child learns to walk by doing it, adults learn by experience. You have to structure a situation where the new employee has a chance to experience aspects of the job without having the burden of performing perfectly the first time. Demonstrate the skill as you want it performed. As you demonstrate, point out the important aspects so that the C.A. understands why each part is important.
Nothing is worse than having to experiment with a new skill on a patient.
Always give the employee an opportunity to practice with you first. Give the employee feedback on what was done correctly. Too often managers only correct mistakes. Positive feedback is much more important in training new skills. Once you have explained what was done appropriately, give feedback on what needs to be improved.