Using osm2pgsql, I imported an OSM extract into a Postgres database. Then I made a layer in in TileMill that contains the data from Postgres. The map was exported to a MBTiles file. At this point, all my transportation features (lines) are on a single layer and my map is terribly unpleasant to look at.
How do I apply the openstreetmap-carto cartocss to my map? I discovered I can create a style for each layer but that seems like a painfully slow way to style my map and I'd need to import each feature onto its own layer resulting in a separate query for each feature line. There's gotta be a better way.
What is the recommended workflow for building a map in TileMill from OSM data in a postgres db?