NOVA12.......When I first read your post I was under the impression you were fishing for roach with your punched bread over liquidised bread and hemp. All of this suggests small hooks and fine fishing and a great way to catch roach...
Then I read another post which says you're after tench, chub, carp and crucians, which, apart from the crucians might need more substantial tackle and POSSIBLY a slightly different approach to catching them and would POSSIBLY bring more fish in the net !
I am NOT saying you cannot catch on your punched bread and your question was ' how much liquidised bread you need for a session ' but I would like to know how you arrived at this method in the first place ?
I would also be interested to know more about the tackle you intend using ( hook size, rod type etc etc ) approximate depth of water in the swims you fancy and if you are fishing on the bottom, off the bottom or even mid water ?? Are you fishing a commercial ? Even time of day might make a difference !
As I've said, your question was only asking about the liquidised bread so maybe I'm asking too many questions outside of this, and if that is the case then the suggestions already given by others are just fine and I don't want to complicate matters !!
It is only my opinion, but to my mind you cannot just consider one factor in fishing without giving consideration to many others...Only my opinion, though !
Good luck, anyway !!