I understand your struggle with the cade lambs, we have had MANY! One trick I find works is once the teat is in the lambs mouth gently put your hand around their nose and gently push up and down (this is hard to explain!) usually the small amount of pressure on their nose helps to encourage them to drink. Another thing I usually try is tickling their tail or just above it which makes them think it is their mum nuzzling them.