Personally? Make a list of all the teams that use your product. Schedule interviews (30 minutes to an hour for initial) with a few that use it the most, and a few that use it less. Ask them what the best and worst parts are. Ask them details about the things they bring up, and prompt about related areas they might be struggling with too.

If you get any repeats from team to team, assume those are systemic issues and try and find a solution.

The hard part usually isn't figuring out the nuances, but rather realizing that someone wants to do something at all and/or can't because of some restriction. Assume you know nothing about how they actually do what they do and listen closely.

1. Find early adopters of the thing you're building who are willing to use and give feedback (bugs, friction logs) in the early stages of the feature.

2. Build relationships with your users / VIP users and meet regularly to discuss friction points and upcoming features (feasibility, etc). To make it time efficient, make sure you're talking to staff engineers who can speak on behalf of a significant portion of your user base. Make sure your team is closing the feedback loop with these engineers (i.e. shipping things that address their concerns) in a timely fashion.