Adding additional shp files?

I have an OSM server setup using osm-bring and it is successfully rendering tiles for an extract of North America. I would like to add additional Natural Earth shp layers (lakes and administrative boundaries) to the whole planet, to better provide orientation for users when they scale out. I followed the pattern used for simplified-land-polygons-complete-3857 and land-polygons-split-3857 but can't get (for example) ne_10m_lakes to show. I am hoping somebody can let me know what critical step I missed out of this workflow:

1. I downloaded ne_10m_lakes, ne_10m_admin_0_boundary_lines_land and ne_10m_admin_1_states_provinces from Natural earth

2. I updated the osm-bright.osm2pgsql.mml to include the new shapefiles. For example:
   {
   "Datasource": {
   "file": "/usr/local/share/maps/style/osm-bright-master/shp/ne_10m_lakes/ne_10m_lakes.shp",
   "type": "shape"
   },
   "class": "shp",
   "geometry": "polygon",
   "id": "ne_10m_lakes",
   "name": "ne_10m_lakes",
   "srs": "+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0.0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs +over",
   "srs-name": "900913",
   "status": "on"
   },

3. I edited configure.py to have an entry for each new layer:
   config["ne_10m_lakes"] = path.join(getcwd(),"shp/ne_10m_lakes/ne_10m_lakes.shp")

4. I recompiled the stylesheet, wiped out my old tile cache, and then rerenderd the tiles.

However, no lakes show…

What am I missing? Do I need to create or update a .mss file to include directives on what color to render the lakes (and boundaries)?

Many thanks for helping a newcomer to the OSM world.

Start by comparing the added entries in osm-bright.osm2pgsql.mml and configure.py with the existing simplified-land-polygons-complete-3857 and land-polygons-split-3857 layers. Then inspect the stylesheet's .mss files to determine whether the new layers have rendering directives; done means the lake and administrative-boundary layers appear after recompiling and rerendering.