How I would I whitewash old red brick; then alternating bricks by painting with white, grey and black enamel
Interior? To whitewash you just use thinned down paint. If latex, thin with water, if oil/alkyd thin with paint thinner. Brush or roll it on when you get it to the consistency you like. Once dry add your accent colors. Have fun.
I did something similar with the brick surrounding our fireplace. Mix 1 part water with 2 parts paint and use a brush or even a sponge to paint. Here's the project that I did. Mine doesn't have the enamel so that would be the difference but you could use any of the colors to "white-wash". Wishing you the best.
Here is a video for white washing, but I don't know what you mean about the enamel paints. If you want to paint them, why whitewash the first. I also don't think that painting them like that would look very good, and it'll be hard to get off if you don't like it.
This may help: https://www.hometalk.com/4242640/painted-brick-fireplace-white-redo