Record stores, the tried & tested analog method.
When you'd have to go through piles of 10 records @ a time cos booth-limits were usually set by pretentious cunts, put the listening batches into piles of yes/no/maybe, go back through the crates, repeat til your fix has been satiated. Spend whole Saturday afternoons traversing cities, London, Bristol. Manchester, Sheffield, Leeds & Nottingham stores, just for that one secret weapon.
Digi? Discogs for cross-referencing labels/artists/musicians, add their Youlube links on the release page, it couldn't get much easier, Bandcamp similar cross-referencing, Gemm has gone but it was brilliant for swapping trade-lists...consistently found golden nuggets by the amount of requests sought for specific releases here n there