Try using a size 16 hook length with a hair and if possible buy a cheap bag of dog mixer for around 3 quid but will last you a long time. Scatter some freebies on surface to get them confident with the bait and then drill some holes before hand in some of the biscuits to make it easier applying them to the hair.
It's up to you on how many you want to use on the hair but I prefer to use 3 as it tends to pick out the larger fish and helps counter balance the hook. It's much more easier if you use a pole as well as you can literally place the biscuit in front of their noses.
Here is a result from last weekend but unfortunately caught the greediest and smallest of the carp feeding.
It also had what looked like a heron attempting to eat it on its dorsal fin.
Good luck
