When I lived in Upstate New York as a child
we ate tons of blackberries.  We simply grazed
off of them.  You must wear long pants and good
shoes, not sandals, no golves.
 Then using the side of your feet
break down a path as you graze.  You should end
up with very few scratches.  Never push the canes
with your hands except to reach in for berries.

Of course, if it is a garden blackberry patch then
you have neat rows like a hedge and don't break any
canes.

R. Keene