They don't call me the charcoal nerd for nothing. Kingsford burns differently than RO. It is less dense with more volatiles (crap that burns) so it will "catch" throughout the pile faster. The con is that it won't last as long and will ash snuff more quickly.
RO is 25% more dense with fewer added volatiles. The heat generated will spread more slowly through the fire, but last longer. RO generates the exact same amount of ash as Kingsford, but won't snuff as quickly. My own head to head test had RO lasting 47% longer than than KBB.
It was the water that brought down your temp, not the charcoal. I've dry smoked with my
WSM with temps in the high 20s to low 30s and had no problem keeping temps up.
Water temp will not increase above 212F at atmospheric pressure. Water absorbs a LOT of heat energy that could be heating your chamber, that's why it is called a "heat sink." Water expands in volume 1700 times when it flashes to 212F steam. That 212F steam condenses when it touches any thing colder. It all acts in a way to keep your chamber temps down.
If you are trying to run at 300F and put water in your smoker, it's like putting a standard carbureator on a 300 mph dragster. No matter what you do, it won't perform as you want.
The majority of experienced
WSM owners have tossed their
WSM instructions and dry smoke. If you do decide to give dry smoking a try, don't use RO like KBB. Use fewer hot briquettes to add to your cold pile for low n slow cooks. For hot n fast, add the same amount.
Let us know how that 5 lb'er turned out!