Meg, I think we need to see it - is it the kitchen, fireplace, flooring? Why do you want to alter it? I'm not at all against German schmear - depending on the home, if it is appropriate for the/your style.
We are installing brick veneer in a couple areas, and I plan to flush the mortar to give it an older look, and add a wee bit of 'schmear'. After which I'll add a bit of antiquing, but only if I deem it needed.
There are several ways to alter brick, as you've mentioned. You need a rather artistic hand for some - to keep it looking authentic. If you do proceed, I recommend gathering as many photos of what you want it to look like first, then attempting it on some separate brick, purchased at a brick yard. Often brick is antiqued ever so slightly by using a mix of very wet plaster and light paint, and gently splattering - before installing. I wouldn't do that after installed, you won't get the same look unless you are exceptionally talented.
Be aware that brick stain will most likely leave your brick a rather dulled, monotone color. This was applied to my front steps after a mortar mishap by a rather horrible tile layer. It eventually faded with weather, but I found the entire look to be unattractive. You might not, but again, test on separate bricks.
Painting the brick seems popular now, though I'm not fond of the look. I prefer the brick pretty much in it's original state.
Do you want to lighten it? Do you want it to look older? What you do depends on your home and the look you want. Choosing something random, just to make a change, most likely will not end in good results.
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Sarah!
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