This study examined how three instructional methods influenced the development of independent learning skills and business presentation performance among 18 college EFL learners with mixed English proficiency levels. Over a nine-week Business Presentation in English workshop, students engaged in one of three practice conditions: (1) an AI-mediated practice model using generative AI tools, including HeyGen, to create avatar-based presentation simulations; (2) a self-recorded video practice model in which learners uploaded and reviewed their own rehearsal videos; and (3) no additional training beyond standard instruction. Three research questions guided the inquiry: (1) Which instructional method produced the strongest presentation performance? (2) Which practice mode proved most suitable for learners at different proficiency levels? (3) How did students perceive the benefits and challenges of each method? Instructor and HR-specialist evaluations indicated that the AI-mediated practice model yielded the strongest overall presentation performance, particularly in organization and delivery. The findings further showed that generative AI tools, which created avatar-based presentation simulations, functioned as highly valued models that students followed to refine their own performance. However, individual differences—including English fluency, level of commitment, and degree of prior preparation—also substantially shaped learning outcomes. Survey and interview data revealed generally positive perceptions of AI-supported rehearsal, especially among lower- and intermediate-proficiency learners.