I've collected a number of hackle pliers over the decades.
Yet, my English style pliers are the ones I use most, by far. So, here I am looking to obtain some more.
Pliers cutting dubbing loops, feathers, flash and whatever through sharp edges. The worst are the bent punched flat spring steel ones with very sharp edges.
If necessary rubber tube pieces work to minimize damage to materials.
Unfortunately, those same rubber, dip additives reduce the finesse English hackle pliers bring to the vise. As does using vise grips to hold them open.
Stoning/filing the edges of hackle pliers reduces sharp edges. Stoning/filing the plier tip surfaces flat greatly aids their ability to grip effectively.
What matters most is ensuring the plier tips are parallel and flat to each other. That they grip evenly. Well, that and grip strength of the pliers. Sometimes, the tips must be separated and spread apart to maintain a pliers strong grip.
If one insists on using rubber cement or dip-it on plier lips, unhook the plier lips and let the pliers spread out, then apply and let dry. Don't use vise grips!