Are the bricks embossed? It's not easy to see in the photo.
If they are, you can firstly daub the surface wth mortar coloured acrylic paint (light greeny grey), making sure all mortar courses are filled.
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Before it dries, wipe off the excess (diagonally) with a paper towel, to leave the paint in the indentations
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Mix brick coloured acrylic paint, keeping it fairly gooey. Then dab a piece of sponge into the paint.
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Take off most of the paint by dabbing the sponge on a piece of newspaper, then lightly dab the sponge on to the surface of the brickwork. Don't press too hard or the paint will ooze into the mortar courses.
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Let it dry and job done.
Rik