Generally I've been harvesting them manually using tools like RGeo or ex_shape.
I also don't see how I could be "doing it bad" since the thing I need to do is to use data from sets that use multiple SRIDs. If I can't reliably pick out the SRID, I also can't reliably bring them all into my DB.
What do you use to ingest Shapefiles into PostGIS? Can you provide an example with files where you failed?