Yes, the files in
/opt/brother/Printers/HLL6300DW/*
installed without problems.
But the files in /usr/lib/cups/*, which are avaiable in other packages ie. HLL6250DW, did not install with this described “deb-method” of the wiki.
After a look at
https://aur.archlinux.org/cgit/aur.git/tree/PKGBUILD?h=brother-hll6250dw
i understand the problem now.