Determining precise and accurate stellar parameters, and in particular ages, is of utmost importance for gaining a deeper understanding of the formation and history of the Milky Way. This is especially true for stars in the galactic halo, which belong to the oldest stars known in our Galaxy. However, due to their distance and scarcity, those targets are often poorly characterized. In this poster, we present preliminary results from our ensemble boutique modeling of red-giant branch (RGB) stars. In an effort to extend the IAC Grid up to the RGB, we construct a grid of stellar models using the 1D evolution code MESA and compute their oscillation modes with the pulsation code GYRE. Using this grid, the individual modes, and a customized optimization procedure, we aim to obtain precise ages and stellar parameters for an ensemble of stars on the RGB, focusing on stars from the Galactic halo. For this purpose, we select samples of well-characterized giants in the halo observed by the Kepler mission, with identified oscillation modes and published spectroscopic parameters. The halo sample is particularly interesting, as for those targets, the ages from literature based on global asteroseismic modeling are significantly (> 50 %) younger than expected for stars belonging to the galactic halo. First, we apply our boutique grid-modeling on a validation sample of stars close to solar conditions to demonstrate the functionality and accuracy of our method as well as to fine-tune it. Subsequently, we use the adjusted code to determine precise ages and parameters of the targets in the halo sample and compare those results with ages determined from global asteroseismology. To put our results into context, we apply our method to a comparison set of stars. With this, we aim to assess differences in age and parameter space between chemically comparable samples in different galactic populations and provide the first ensemble boutique modeling for stars in the outskirts of our Galaxy.