If your brickwork isn’t painted already, don’t do it.
Personally I don’t like the look of painted brick. It has the look of indulgence, like someone just discovered paint and couldn’t stop themselves.
Bricks are beautiful if they can be seen. Most of them are, at least. But there are reasons other than aesthetics not to paint bricks.
Bricks need to breathe.
But well ok, if they’re already painted, then use a breathable paint to repaint. These are usually water- based paints that allow moisture out, but not in.
Sometimes you will see glazed bricks, which were often used within an enclosed well area of a building to make it brighter and more attractive. How can these traditionally built walls of glazed bricks breathe, you may ask? Well, they will breath through the pointing between the bricks, if it is soft enough, as it would have been when first built.
So you can see that when bricks are painted (pointing and all) all around a building, this can create a real problem as I once saw in Surrey. The few airbricks around the building were clogged, and we tried cleaning these out, but even unclogging the airbricks didn’t solve the problem.
Painting bricks is a permanent thing, or might as well be considered permanent, given the cost of sandblasting ( risking damage to the brick) and the necessary repointing afterwards.
So don’t paint unpainted bricks, the people living in your house in one hundred years time will not think well of you.