I forgot to add using larger electric drills is the done way of providing the reverse drive in the domestic environment.
Hello
Mod BB, Millzy and
Norm ... and all
Thanks Norm for raising this topic.
Yes, a domestic drill with a suitable connector is fine.
But the drill must be capable of
low rpms!Also consider a manual Brace tool - nothing wrong with that!
The grinding paste must be able to
do its job.
Higher rpms merely throw the paste centrifugally outwards, sometimes amusingly so.
We don't want Jackson Pollock results here!

In the old days, back-lapping was all manual (see below).
The reel was rotated by hand, usually on a jig (for the smaller mowers).
In the 19th Century 'Lavender Paste' was used.
This was replaced by graphite compounds in the 20th century.
Slow is the way to go for great results.
Back-lapping should be conducted regularly (at least once a season).
Back-lapping is
not a procedure that can be effective with poorly maintained machines.
The only option, then, is re-grinding of reel, and grinding (or replacement) of the bedknife.
[1] Back-lapping involves the reel operating in
reverse.
[2] The reel
must make slight contact with the bottom blade (bedknife).
[3] After the lapping, all paste needs to be washed-off!
[4] Checking results should be made via the 'paper-test method'
[5] The machine should
not be run with any trace of grinding paste.
[6] Only water-based grinding compounds should be used.
Hope this helps-----------------------------------
Jack