  Context. The third Gaia Data Release, which includes BP/RP spectra for 219
million sources, has opened a new window in the exploration of the chemical
history and evolution of the Milky Way. The wealth of information encapsulated
in these data is far greater than their low resolving power (R=50) at first
glance would suggest, as shown in many studies. We zero in on the use of this
data for the purpose of the detection of ''new'' metal-poor stars, which are
hard to find yet essential for understanding - among other - several aspects of
the origin of the Galaxy, star formation and the creation of the elements.
Aims. We strive to refine a metal-poor candidate selection method which was
developed with simulated Gaia BP/RP spectra, with an ultimate objective of
providing the community with both a recipe to select stars for medium/high
resolution observations and a catalogue of stellar metallicities. Methods. We
used a datased comprised of GALAH DR3 and SAGA database stars in order to
verify and adjust to real world data our selection method. For that purpose, we
used dereddening as a mean to tackle the issue of extinction, and then we
applied our fine-tuned method to select metal-poor candidates, which we
thereafter observed and analysed. Results. We were able to infer metallicities
for GALAH DR3 and SAGA stars - with color excesses up to E(B-V)<1.5 - with an
uncertainty of 0.36 dex, which is good enough for the purpose of identifying
new metal-poor stars. Further, we selected 26 metal-poor candidates - via our
method - for observations. As spectral analysis showed, 100% of them had
[Fe/H]<-2.0, 57% had [Fe/H]<-2.5 and 8% had [Fe/H]<-3.0. We inferred
metallicities for these stars with an uncertainty of 0.31 dex, as was proven
when comparing to the spectroscopic [Fe/H]. Finally, we assembled a catalogue
of metallicities for 10 861 062 stars.
