If you haven't seen it, check out the documentary film Desperate Man Blues.
Source: IMDB
You want to see hunting for old records? Here's your man, and he has some great tales to tell in the film of heading out into the countryside and knocking on the doors of old black families living in wooden shacks, trying to find out of they might have some even older records stashed in the barn or under the bed. Watch this and you realise that it could just as easily relate to the hunt for rare soul vinyl. In fact, there is no difference. The hunt is the same, and so are the hunters - the genre is irrelevant.
Just found a trailer for the film on YouTube. In it, Jo Bussard talks about record finds including one which netted him the only known copy of a particular 78, valued, he says, at US$50,000.