Begin by exporting the necessary data from Braze. Access the Braze dashboard and navigate to the data export section. You can use Braze's REST API to export data. For instance, use the `users/export` API endpoint to extract user data in JSON or CSV format. Make sure you have the relevant API keys and permissions to perform the export.

Once the data is exported from Braze, ensure it is properly formatted for insertion into PostgreSQL. If the data is in JSON format, consider converting it to CSV or another tabular format that PostgreSQL can easily process. Clean the data to remove any unnecessary fields or format inconsistencies.

Ensure your PostgreSQL database is ready to receive data. Create a new database and table structure that matches the schema of your Braze data. Use SQL commands to define tables and columns, taking into account data types and constraints to match the Braze dataset structure.

Before importing, transform the data to align with the PostgreSQL schema. This may involve mapping fields from Braze to your database's fields, converting data types, and handling any discrepancies. Use tools or scripts to automate this process if dealing with large datasets.

Use PostgreSQL's `COPY` command or `INSERT` statements to load the transformed data into your database. For CSV files, you can use the `COPY` command as follows:
```
COPY your_table_name FROM '/path/to/your_file.csv' DELIMITER ',' CSV HEADER;
```
Ensure that the file path is accessible by the PostgreSQL server and that permissions are set correctly.

After loading data into PostgreSQL, verify its integrity and accuracy. Run queries to check for discrepancies, such as missing values or mismatched data types. Compare sample records from Braze with those in PostgreSQL to ensure consistency.

To streamline future data transfers, consider writing scripts to automate the extraction, transformation, and loading (ETL) process. Use shell scripts, Python scripts, or cron jobs to schedule regular data transfers. Ensure that your scripts handle errors gracefully and include logging for monitoring purposes.

By following these steps, you can efficiently move data from Braze to a PostgreSQL destination without relying on third-party connectors. Each step allows for manual control and oversight, ensuring data accuracy and integrity throughout the process.