Designing a Dew Heater
6W sounds like a good staring place for your experiment, but I would use more resistors run at a lower power.
buy 100 cheap resistors and connect most of in series and see if that's good
GW at 5V is 1.2A  so 41.7 ohms total so
maybe start with 89 0.47 ohm resistors in series.
by connecting them in series there string will be more flexible.