Smart as paint
Modern usage should be an insult. Just add "literally." Original meaning from the 1800s: clever or intelligent. First said by Long John Silver, a pirate (an occupation known for excellent grammar?) in "Treasure Island." But how smart is paint, really?
If your target researches the phrase, dictionariies only have the original, complimentary definition --- which becomes a sneaky insult if you add "literally."
If your target researches the phrase, dictionariies only have the original, complimentary definition --- which becomes a sneaky insult if you add "literally."
You're as smart as paint, literally. Don't be offended. I was just paraphrasing a compliment from "Treasure Island." It's a literary classic.