I've been using this method for over a year, as I was saving for my WSM. I foiled the bottom grate, used two firebricks slightly offset, loaded kingsford with wood chunks mixed in, and let 'er rip using a modified minion method, lighting a dozen or so coals to start.
I began with a water pan simply because I did not read thoroughly enough here to know it wasn't necessary. I didn't think 7-8 hours in a kettle with no water pan would be ok. I used a 13x9 foil pan, because I didn't want any meat directly over the coals anyway. I had to bend the edges a little for fit.
I used the foiled charcoal grate and a rib rack to have a "first story" smoke of ribs, chicken legs or whatever. Temps were 20 degrees cooler down there than at cooking grate level. I did a 9 pound butt once, then tended to get 8 or 9 pound butts and half them for the main grate. Also did brisket, and almost always threw a few sausages on any unused grate area.
The lid temps were 20 to 25 degrees higher than the cooking grate, for a total differential of 50 to 55 degrees between top and bottom of the 22" platinum kettle. I got a maverick smoker probe to monitor chamber and meat temps, which made it all possible.
Water needed to be added every 3-4 hours. I used an electric tea kettle to bring the water to boiling before adding, and between the firebricks and water pan, and hot water, temps stabilized in 5 minutes or so. Coals were added or stoked at water intervals. I will likely try it without the water pan while awaiting Amazon's delivery of my new WSM.
A bit more work than a wsm, but the awesome results brought the wife onboard the wsm wagon. Only a couple more weeks...