[PJ]

Depends on what the smudges are from.

I've had success cleaning a hat before using a toothbrush, and a TINY drop of dish soap. Wet the soiled spot and gently scrub and rinse. I used dish soap because it's a lot stronger and harsher than liquid laundry detergent, so for concentrated spot cleaning, I figured dish soap + light scrubbing would give me a better chance of saving my garment than liquid deterg + hard scrubbing.

Try at your own risk. But if your hat is ruined with the smudges anyway... you have nothing to lose.