It's all in the prep work, Lisa:
With a sprayer or fuzzy roller and brush.
Hi Lisa, here's an article that you might find helpful.
I recommend using masonry stain instead of paint.
If it's interior consider whitewash? It's easy and CHEAP. I 'washed" our monster interior wall a couple years ago. Posted the project here on Hometalk
"Massive brick fireplace wall whitewash success"
Here's a sneak peak