To gather and analyze replies from a specific brand's Twitter account, you can use several tools and approaches. Here are a few options:

1. Tweepy (Python Library)
Tweepy is a Python library that interacts with the Twitter API. You can use it to collect tweets and replies from a specific user.
2. TAGS (Twitter Archiving Google Sheet)
TAGS is a Google Sheet template that allows you to set up and run automated searches of Twitter. You can use it to collect tweets and analyze them using Google Sheets.
3. Brandwatch or Hootsuite
These are professional social media analytics tools that offer in-depth analytics and tracking capabilities. They can track mentions, hashtags, and interactions on social media, including replies to tweets.