Boundary representation (B-rep), as the standard for CAD modeling in modern industrial design, typically features complex geometric and topological structures, making direct tool path planning for B-rep models rather challenging. Existing research primarily focuses on iso-scallop tool path generation for single parametric surfaces, achieving high machining efficiency on individual surfaces but struggling to be directly applied to B-rep models with complex patch layouts. Mainstream commercial CAM software also faces technical limitations when processing complex models, such as numerous process parameters and strong reliance on manual intervention. To overcome these limitations, we propose an optimal tool path planning method for B-rep models with minimum tool retractions. The method aims to minimize programming effort while ensuring machining efficiency, generating a complete 3+2-axis finish machining solution for the entire B-rep model in a single step. The algorithm first segments the B-rep model into machining regions by solving a minimum cut on a weighted graph constructed from discrete collision detection results, ensuring a consistent machining direction within each region. For each region, we project the patch onto a plane, build an adaptive iso-scallop height mesh, and generate a single start-to-end tool path using a minimum spanning tree (MST) algorithm. Finally, the complete machining path for the entire model is obtained by optimizing the transition path lengths. Experimental results demonstrate that our method can stably generate complete model paths, and compared with mainstream commercial CAM software such as UG NX, it achieves competitive performance in both programming and machining efficiency.