I got my osm2pgsql/PostGIS/Mapnik/Nik4 setup up and running. I have tested it with the openstreetmap-carto style and everything works well. Now I want to change the style to Mapbox' pencil style (https://github.com/mapbox/mapbox-studio-pencil.tm2). I am not sure how to do that as this style does not have ".style" file that I could use with osm2pgsql. I have tried leaving data exported using openstreetmap-carto and exporting using Nik4 using the "project.xml" file. This only gives me the background image with nothing on it.
I guess I need to import the data to PostGIS with the correct style. How do I do this when I do not have the ".style" file? Or is it possible to do it without importing using the specific style?