Combine beer, vinegar, ½ cup seafood seasoning, and salt in a large stockpot over high heat; bring to a strong simmer.

Carefully place each crab upside-down and stick a knife through the shell just behind the mouth right before cooking.

Fit a screen over simmering beer mixture; layer crabs on the screen.

Cover the pot; steam crabs until they turn bright orange and no blue-green color remains, 20 to 30 minutes. Sprinkle crabs with remaining ¼ cup seafood seasoning before serving.