When I have questionably old eggs (we’re talking three months or more here - and I’ve only found 2 bad eggs in 20 years, one sulfured and one simply dried up), I use a two-bowl cracking method. Crack each egg into a small bowl, give it a sniff and then, if it’s okay, dump it into your food prep bowl. Repeat with the next egg. This way, if only one of your eggs is off, you won’t contaminate your whole batch of brownies. Just pitch the bad egg (put it in a snack or sandwich sized ziplock so it doesn’t stink up your trash) and wash the small stinkified dish before proceeding.
Same thing when separating eggs for a meringue or foam - use a small cup to separate one egg, then dump that white into a larger bowl. That way if you get a smear of yolk in it, you’ve only lost one eggwhite, not a whole bowl of them.