One of the more underutilized tools within Google Docs, Slides, Drawings & Sheets is the Paint Roller (Paint Format) Tool. It’s purpose is simple – when you want some text or an object to be formatted just like another set of text or an object, the Paint Roller is the tool that you need. Click once on the already-formatted object/text, then on the Paint Roller and then on the to-be-formatted object/text.
I’ve posted before about how it works in Google Docs, but I wanted to share an animated GIF about how it works in Google Slides! Notice that it works on text boxes, as well as on shapes, lines and images! With text boxes, you can even apply it to certain words in the box rather than the entire box.