What are the best techniques for cleaning a flagged bristle paint brush to ensure its longevity and optimal performance?

To clean a flagged bristle paint brush effectively, first rinse it in warm soapy water, then gently comb out any paint residue with a brush comb. Follow up by soaking the brush in a mixture of water and vinegar to remove any remaining paint. Finally, reshape the bristles and let the brush air dry completely before storing it upright to maintain its shape and prolong its lifespan.