Once you get into the flow they can be knocked out pretty efficiently, as long as there aren't inconsiderate drivers lingering with their cars at pumps.
I recently ran into a glitch trying to do real-time reporting and taking a picture within SASSIE in the report. My Safari screen would go to black when I accepted the photo, with no way to recover but to quit the app. Cost me an extra 20 minutes at the location where it first happened.
So your strategy of grabbing photos and completing in the car is absolutely the way to go.
As long as I've revealed, and the cell connection is decent, I have no problem hanging out on the spot. It's also a good way to ensure you get all photos you might need.
If it's one of the conditional reveals, and I'm parked in a conspicuous spot, I will move on to the next available parking lot on the right and wrap things up there, provided I'm on schedule.
When doing a bunch of those I may let them pile up after getting something saved for each one, and submit them in reverse order from my phone when I have a prolonged stop for a meal or at the end of the day.
For the brands that require photos of all pumps, I will try to get as much of the report done onsite as time and cell coverage patience allow, but I will always wait to submit pump photos when I can work from my laptop.
Way more efficient to have multiple windows open so I can drag and drop photos, and larger icons make it easier to see things.
Have synthesizers, will travel...