In this session, I will share how I use OpenAI's ChatGPT to create custom "digital course assistants" for both my mathematics and math education courses. These assistants generate course materials such as assignments, quizzes, and lecture notes, and are also made available to students for personalized learning. I will detail the prompt engineering methodologies I use to tailor the GPTs for specific educational needs, ensuring clarity in mathematical explanations, optimizing accuracy, and enhancing learning engagement. By highlighting practical strategies for prompt optimization and creativity in teaching, this session will provide attendees with insights on how to effectively integrate AI tools into education, offering both production-ready applications and experimental possibilities.