Well Geez...Looking back I have practiced several types of hand forms. I am most comfortable with Shoji Nishio's example. Fingers together.. thumb tucked in (hidden)... Ki extended through the forefinger.
Two basic movements both circular...picture "washing the inside of a bowel or cylinder movement and the hour glass movement ( big to small or small to big cylinder)
There are some pretty good illustrations in Sensei Varjan's "Nishio Sensei Aikido Notebook 1." but I won't post them here without Sensei Varjan's permission.
To summarize your hand is basically an extension of your sword.
William Hazen