Although the brother website has instructions for debian/ubuntu 64bit they only actually work for ubuntu (actually they might not even work with the latest ubuntu) ... on debian the instructions should be more like this:
Enable multi-arch for 32bit
sudo dpkg --add-architecture i386
Install cups 32bit libs
sudo apt-get install libcups2:i386
Download the lpr and cups drivers from brother and install them:
sudo dpkg -i ~/Downloads/hl3040cnlpr-1.1.2-1.i386.deb sudo dpkg -i ~/Downloads/hl3040cncupswrapper-1.1.2-2.i386.deb
You should be good to go if you device is connected via USB, otherwise you will need to go to your local cups and reconfigure the printer to the proper uri.