Watch how to How to Quickly Copy Formatting in Google Docs:
To do so:
- While using a Google Doc or Spreadsheet, format a line of text or cell in your desired appearance.
- Click the Paint Format icon on the left-hand side of the tool bar.
- To apply this format to other text, simply highlight or click.
- Double clicking the icon will lock the format into place and every piece of text clicked will change to the new format.
Reference - Google Gooru - How to Quickly Copy Formatting in Google Docs