Ok, I lied...Ramlan-sensei mentioned a third very important point yesterday - Atemi (striking).
This opens almost all of the Yoshinkan arsenal and is an essential part of the technique.
Atemi, the opening strike, is designed to stop uke's forward motion and set their weight back on their heels (off of the balls of the feet). That means it must be done hard and fast, with full intent and full forward projection. Weak atemi is pointless.
A strong atemi should lock uke's blocking arm into place and drive through the arm into uke's hips and feet. Uke should be unable to withdraw the blocking arm. Shite's atemi should be right in uke's face leaving uke no time to do anything except block.
This cannot be done if shite has any backward motion at all from the beginning of the technique. The initial motion of shite should be explosively forward, along the line of power, and applying atemi with projection through uke's head. It is worth noting that for advanced students, this initial explosive motion is also DOWN, lowering the hips and drawing the connection to uke's center of balance onto them.
Sensei says O-Sensei maintained that aikido was 70% atemi. I believe this, given its purpose to disrupt uke's balance. Atemi is worthy of careful consideration and diligent practice.