I sometimes wish I could just format my documents with mind control. But until I develop that power, there are several options. Styles. The toolbar. And to speed things up once you've done things right, the Format Painbrush icon.
So. This is how it usually works.
And click the Format Paintbrush icon once
So to keep formatting as long as you want, then select the formatted text like you normally would, then doubleclick the Format Paintbrush icon.
Click the Format Paintbrush icon once when you're done to stop the formatting.