The instant disclosure relates to methods and kits that improve the cosmetic properties of hair, especially hair treated with a chemical relaxer composition. The methods entail treating hair with a combination of different hair-treatment compositions. For example, hair (especially chemical relaxed hair) is treated with a hair-treatment composition comprising at least 0.5 wt. %, based on the total weight of the hair-treatment composition, of at least one non-polymeric mono, di, or tricarboxylic acid, and/or a salt thereof; one or more amines; and water. The hair is subsequently treated with an auxiliary composition, which includes one or more polyurethane latex polymers. Hair treated according to the disclosed methods, especially chemically relaxed hair, exhibits improved style-control and discipline, frizz control, smoothness, softness, and strength.