Achieving straight lines in painting requires a combination of essential tools and techniques. Brushes, straightedges, and painter’s tape are crucial for guiding and defining lines. Prepare surfaces by priming them for better paint adhesion. Master the use of a straightedge by aligning it along the desired path and guiding your brush. Control paint viscosity and unload excess paint to prevent bleeding. Practice regularly to improve accuracy and achieve crisp, straight lines that enhance the overall quality of your painting.