No that's about right. My initial pre campaign prep was read the book and understand the factions, session zero to see what themes my players wanted to explore and what factions they were interested in interacting with.

Between sessions I only needed about 10 minutes to think about the next game, who was the job against, who's upset or happy with the crew currently, what factions plans are the players ignoring so are progressing unopposed and what does that look like. Was there any fallout from their last job. The way the city is set up every time your crew gets ahead it will please someone and upset someone else I found that made prepping super easy. Then all I needed was a list of random names for NPC's and I was happy making stuff up on the fly for the most part.

Some of them bigger things needed more thinking and prep like when they broke into the ghost hunters headquarters (I can't remember the name, guys follow the death crows and wear masks), that needed a little more time. Or when they accidentally summoned a demon I needed to work out what it wanted and how it worked. Side note demons are excellent fun and should be terrifying forces of nature in blades.