here are a number ideas on Hometalk:
PAINTING or WHITEWASHING:
Hi Jeanne, this article will help you paint your brick hearth - https://www.bhg.com/decorating/fireplace/styles/how-to-paint-a-brick-fireplace/
Here's a post that might help - https://www.sherwin-williams.com/homeowners/inspiration/project-center/how-to-paint-a-fireplace
Hello. This is an exciting project that I’ve been thinking about too. Here’s a link that could be Informative —-hope this helps.
Painted brick fireplace
you're going to need to prime and then paint to avoid bleed through
You may want to consider staining rather than painting. Stain has MUCH less ongoing maintenance requirements whereas paint will need to be redone every year or two.
Clean first with TSP then you will be ready to prime and paint. Make sure your paint is good for masonry.
Excellent directions here!