Our team charge time at an hourly rate. We only estimate, never quote, so it's important to keep clients updated on where things are sitting and let them interact on tasks when testing and reviewing.

In the end, after trying a few of the popular apps, we decided to build our own. We've been using it and evolving it for 5 years and are just now launching a beta and trying to see if others might be interested

https://tasman.io/

https://vimeo.com/223398703

In my experience, all the features can be met by different apps but I haven't seen anything yet that handles the end-to-end workflow and has a nice user interface for users and end clients

What do you use? for client interaction -> project and budget tracking -> task tracking -> time entries -> billing