"No, duh" in Chinese?

How do you say the different shades of “duh” in Chinese?

“Duh…” (I’m to stupid to think of a word)

“Duh.” (You’re stupid. This one is said in American English with a tone reminiscent of Chinese 2-2, like “德額”. Without the tones, you could say, “No, duh”)

I don’t think it works quite the same way.

The first thing that comes to mind for the “I can’t think of the word” thing is using nei4ge…nei4ge…nei4ge repeatedly until the other person listening to you fills in the word in desperation.

I can’t think of an equivalent for the other usage.

I’d say “fei hua” or “pui-oe” (sounds better in Minnan) for the second one. I know it’s not a direct translation, but it gets the point across.