If you already have the film and need the subtitle file specifically:
In Russian, the title is usually translated as (Prigorshnya prakha). When searching on Russian-specific platforms or trackers, using this title will yield more direct results for both subtitles and dubbed versions. A Handful of Dust subtitles Russian
: This is the most comprehensive database for subtitle files. You can search for "A Handful of Dust" and filter by the Russian language to download the .srt file. If you already have the film and need