Was it important to surface quickly?

There usually was no reason to hurry. The OOD (or captain) would take his time in order to surface safely.  The boat would come up to periscope depth carefully. The OOD wanted to be sure that there was no danger of collision with other vessels and, in WW2, no immediate danger of attack by the enemy. Then, when they saw nothing through the periscope and heard nothing on sonar, they dumped air into the ballast tanks.  They also put rise on the planes. That brought them to the surface.

However, if they would be going to battle stations guns in WW2, they would want to surface very quickly. Coming up to periscope depth was still done carefully. Then, when it was nearly time to surface, some air was added to the ballast tanks while the planes were holding the boat down. Then, when the command to surface was given, the planes went to full rise and more air was dumped into the ballast tanks. The goal was to get the first rounds fired in less than a minute after the order to surface was given. The target was likely to be shooting back, so speed and surprise were of the essence.

Many things needed to be done to fire the first rounds in less than a minute:

1. Enough air had to be dumped into the ballast tanks to get the main deck out of the water.
2. Gun crews needed to open hatches and assemble on deck.
3. The gun(s) needed to be unsecured. (They were tied down so they would not make noise when submerged.)
4. Ready storage for ammunition had to be opened.
5. The gun(s) had to be loaded with the ready ammunition.
6. The gun(s) had to be aimed.
7. The gun(s) would be fired when the boat was steady enough.