For anyone who may have issues with proprietary driver, this info may be helpful (if there is a foo2hp driver for you):
Found this page (http://foo2hp.rkkda.com/) for my driver and followed instructions from it in the docker console.
wget -O foo2zjs.tar.gz http://foo2zjs.rkkda.com/foo2zjs.tar.gz
tar zxf foo2zjs.tar.gz
cd foo2zjs
make
./getweb 1215 # Get HP LaserJet CP1215 .ICM files
make install
make cups
This resulted in CUPS application being unresponsive with no working password. I restarted the container and was able to now add the printer with the foo driver. This was all done directly in the container so most likely this will not persist if I update the image, but at least its working for now.