1. plugged the USB cable from the printer to my laptop
2. wajig install cupsys foomatic-db-engine
3. sudo ln -s /usr/bin/foomatic-ppdfile /usr/lib/cups/driver
4. On http://localhost:631/ I added the new printer in cupsys, it showed my printer over USB, I selected it and then I chose the correct PPD.
And everything just works. The only nontrivial part is the step 3, that was suggested in /usr/share/doc/foomatic-db-engine/USAGE.gz:
If the printers of the Foomatic database do not appear, check whether the
link to foomatic-ppdfile is in /usr/lib/cups/driver:
lrwxrwxrwx 1 root root 25 Apr 19 18:13 foomatic -> /usr/bin/foomatic-ppdfile
If not, create it manually.
Without it, I didn't see the right PPD in the step 4. Maybe it'd be a nice idea to do this automatically (either when installing foomatic-db-engine or cupsys), or am I missing something?
As to the PPDs, one can get all printer IDs by:
$ foomatic-ppdfile -A
and the PPD for my printer by
$ foomatic-ppdfile -p Minolta-PagePro_1250E
However, it's not necessary in the above howto.