Used it a few times over the years Dave as a paste base with success for Barbel/Chub/Carp and limited success with Tench.
How i've prepaired it was stuff it in the blender and then add some fishmeal (as the binder) and form a paste.
Also tried the following
Heart....(not much success)
Kidney...(as above)
Brains...some success with Tench
Fresh Blood (from butcher) great additive for Tench
Never had any interest when the above fished in chuncks only when used as a paste have they worked.
Malc
Fish with Friends @ MaggotDrowning.com