While performing any energy practice, meditation, or chanting we sit calm and peaceful to feel the BLISS. The same is with VK, slow rotations, or still hands, both help in the same way. This also helps in getting connected to your inner self and guidance from the Universe and you can feel the BLISS.
With slow rotation, you may even feel the energies passing by VK towards the receiver. Sometimes the receiver gets charged before time. If you do rotation slowly, you can feel that fullness in the form of repulsion from the receiver e.g. sometimes we do just 5-6 rotations on water and get the immediate repulsion as a sign of complete charging.