In my experience, it is DEFINITELY a 4 hander job!

The person holding the cat needs the towel wrapped around the cat OR clip the nails before you start this. ALL 4 PAWS..

The person holding the cat should have one hand holding the nape of the neck and pull upwards slightly. This will immobilize most (not all) cats. Don't pick the cat up from the nape like a mom cat picks up her kits - once they are full sized, this will hurt the cat. But the same action still works to stop them moving. Then the person putting in the drops has to move fast!

Good luck.