Corey, you can disregard the last part of this post, I just realized you already have a WSM.
With that said: If I were you I would not bother attempting low & slow in your kettle, except for the novelty of just being able to say you have done it!.. the WSM is so much better suited for the low and stuff, it is not even funny!
I used the Smokenator 1000, It is essentially just a baffle to isolate your fire, from your food.
here is the link to their website:
http://www.smokenator.com/
I had real good success using it, I actually learned how to smoke with it.
As far as vent/damper settings go, the instructions on their web site,
http://www.smokenator.com/instructions.htm work very well to control the fire in a kettle.
I don't mean to sound like I am endorsing that product, but I can say that if you follow their instructions, it does work!
I did find that its tiny little water pan "heat sink", is not big enough for me, it would need refills about every 70-90 minutes. And a heat sink is a definate must to achieve low and slow in a kettle. If that little pan ran dry, temps would spike to 350-375 in no time, and getting it back down is then a challenge. I would remove that little waterpan, and placed about a 4 qt. stainless steel pan filled with water directly on the cook grate above the hole where its water pan went.
There are a lot of threads here where members have made there own baffles, and or use fire bricks to hold the coals to one side, and the fire Bricks also function as the heat sink instead of a water pan!...
Check Out the Smokinator site, and read his instructions regarding the vent settings, it will give you a good baseline of where to start from!..
You will need as "Tight" a kettle as possible, you don't want air getting in from anywhere except your bottom dampers, this will be essential if you are trying to achieve 225-250 temps.
In case you do not know this already: Do not think of the charcoal as your fuel, think of it as only a catylyst to aid the burning of oxygen, the oxygen is your fuel, if you can control the oxygen intake, you can control the temperture. (providing your food is isolated adaquately from the fire, and you have an adaquate heat sink)
I have seen many different set ups other than using the Smokinator, how well they actually work, I do not know, because I went with the Smokinator!
The best advise I can give you however. is: Get a WSM, and forget all of the above. Any of the above requires a lot of attention, and that can be fun, but I like to do overnight cooks, and I like to sleep!... Life is a lot easier with a WSM !... I used my described setup for two years before I got my WSM, and I could not believe the difference, it is pretty much set it and forget it. On long cooks, once the lid is on the WSM, I don't even peak inside the thing for 8-10 hours
They got this thing out there called Craigslist, I think you might be familiar with it
, if you see a deal on a WSM go for It...