Just for the benefit on anyone wondering which path to take in a similar circumstance, here are some notes from today's attempt to get my Brother MFC-7340 printer working in DSL. It only took me an hour, that's pretty good for setting new things up with DSL. Note that this method does not use CUPS, I haven't tried using CUPS in DSL, though it is available from the MyDSL Repository.
The instructions here on the Brother website (http://support.brother.com/g/s/id/linux/en/instruction_prn3.html?c=us_ot&lang=en&comple=on&redirect=on) do actually work for DSL (once you eventually find them...).
The one exception is that dpkg has to be run as root, and the /var/spool/lpd/MFC7340 (the name of the last directory will depend on your printer model) ends up being created without user permissions. This means that when you try to print, lpr will come back with something like:
MFC7340@box: printer 'mfc7340', chdir to '/var/spool/lpd/MFC7340' failed 'Permission denied'
The same error is also generated when the "lpc status" command is tried, which normally shows you the status of configured printers.
To fix, simply use chmod to make the directory for your printer open to all users (as root):
chmod a+rwx /var/spool/lpd/MFC7340
And don't choose this moment to forget that folders need to be marked executable, like I did at first!
Now printing should work from all applications, and directly from the command line for text files with "lpr":
One note about the MFC-7340 Driver (V. 2.0.2-1, 25/06/2008, http://support.brother.com/g/b/downloadlist.aspx?c=au&lang=en&prod=mfc7340_us_as&os=128):
I've found that on some long or complex files, the printer seems to stall on a page and coat the rest of that page with random vertical lines, before continually spitting out blank pages until the print job is canceled at the printer. This also happens in Knoppix 7.2 (on the same PC) where I have the same driver installed via CUPS, so I expect it is a driver problem. In any case it happens quite rarely. I couldn't find any alternative drivers that worked when setting it up in Knoppix.
After this problem occurs, I've found all print jobs are printed blank until the printer is reset (turned off and on).