The spark plug getting wet from dew has nothing to do with flooding as such. However, if yor spark plug cap does not keep dew away from the actual electrical connection (cracked or otherwise damaged) where the plug wire connects to the top of the plug your plug simply won't spark. The spark energy will be grounded through the water path.
Your motor shouldn't flood unless you over choke it when starting, or unless you leave the fuel petcock turned ON when not riding. Also, your petcock may not turn the fuel off completely even if you turn it to OFF if it is old and worn out internally.
If a motor is flooded, hold the throttle wide open and crank/pedal the motor to unflood it. Even better, do this with the spark plug removed. This dries the excess fuel out of the crank case and combustion chamber.