L-shell x-ray fluorescence (LXRF) is a non-invasive approach to lead (Pb) concentration measurements in human bone. The method is based on the detection of the characteristic x-ray photons of Pb at 10.5 and 12.6 keV and experimental studies were designed to perform in vivo human bone Pb measurements. In later studies, however, the initial LXRF methodology was shown to have poor accuracy and precision. In a recent publication, we investigated an optimal grazing-incidence position (OGIP) approach using a submillimeter x-ray beam from an integrated x-ray tube and polycapillary x-ray lens table-top system. The OGIP method effectively reduced the x-ray scatter and produced a Pb detection limit of ~5 μg/g for a 2 mm soft tissue phantom thickness. In this study, the OGIP methodology was improved by using 10 s x-ray spectra acquisitions at sequential positions 0.5 mm apart. The measured Sr Kα peak height versus position data was used to spectroscopically identify the bone phantom and the OGIP. The data was fitted with the analytical convolution between a Gaussian and an exponential decay. The position corresponding to the maximum of the fitted convolution function was then selected as the OGIP. Four phantom sets were used. A cylindrical plaster-of-Paris bone phantom doped with Pb in a concentration of 74 μg/g was used as a bare bone phantom or with one of the three overlying polyoxymethylene cylindrical shell soft tissue phantoms of 1, 2, and 3 mm thickness. The reproducibility of the OGIP method was assessed in five independent trials using each of the four phantom sets. The coefficient of variation (COV) percentage values of the Sr Kα peak height measurements were below 5%. The new procedure decreased by more than threefold the duration and radiation dose of the earlier approach.