The effect of a proper shaping of the temporal envelope of isolated pulses in slow-light systems based on stimulated Brillouin scattering in optical fibers is studied and experimentally demonstrated. The pulse shape can be optimized to lead to a substantial enhancement of the delaying effect. The spectrum of the optical pulses is engineered so that the spectral width of the pulse is minimized while preserving the pulse duration, making possible to match at best the Brillouin spectrum. Exponentially shaped pulses show the minimal FWHM spectral width and experience the largest time delay when compared to Gaussian or rectangular pulses.