I have done a lot of smoking in my weber kettle, pork butt/shoulder, ribs, brisket, etc. I use one digital remote probe, and my gas weber's dial thermometer. I use a cork plug with hole drilled and insert the plug in one of the top vent holes to hold the probe or the dial. The probe can at first be used at grate level then later in the meat.
I have played with several methods of charcoal, from starting with a heap in the starter can then adding unlit charcoal, or adding pre-lit briquettes. As you can see below, all the briquettes are stuff in the side thru the hinge grate. I usually start with about 3/4 starter can, and then add briquettes during the cook.
Smoking with a weber kettle requires a lot of tending. It's hard getting the temps right. I pre-heat to about 300 before adding meat, when meat is added temp drops. Then I start closing the bottom vents until achieve the desired temp range 225-250. The bottom vents on my model each close individually. I always keep the vent close to the charcoal closed and adjust the other two. One way to prevent losing all the heat when adding wood or charcoal, instead of pulling the lid completely off, slide the lid and rest on tray, and quickly add wood or charcoal. I have the hinge open always to do this quickly when opening lid.
Don't forget to either use drip pans or line the inside with alum. foil.
I now happily own a MES and no longer worry about temp control, and get sleep now when cooking in the wee hours.
Hope the below construction helps...

I fashioned my own
smokenator out of a heavy duty baking tray. Note, this was done one night in the wee hours in haste, I have been using it for a couple of years, always intending to improve it, but never did.

*You must have the newer top grate that has the flip up sides so you can easily add charcoal and wood.
Step One: Use a tape measure and measure the length necessary to push through both grills and and still clear once the lid is on the kettle. My length is 13"
Step Two: Cut a 3/8" about 7.5" or 8" up the center, (my cut was too wide). This is so you can insert through top grill. Then widen the cut at the bottom so the tray can be inserted through the charcoal grate whichs has two supporting cross members instead of one like the top grate.
My cutting error was a result of too much beer.
*I insert my tray at an angle 1 row behind the top grate hinge, and angle down toward the charcoal grate two rows in toward the center. If you insert tray straight the width of tray is two wide. I insert the tray as close to hinge as possible on the top grate, this gives me maximum cooking space.
Step Three: Measure the bottom grate opening. The bottom charcoal grate on my kettle has two center cross supports about 1.5" apart. If I was going to do it again, I would cut a piece of cardboard and lay it on the bottom grate, center with the edge where I want the tray to go thru the charcoal grate, then draw my marks on the cardboard template, then us the template to make my cuts.
Due to my cuts being so bad, I lift the top grate insert the tray and then wrap the tray with a few wraps of alum foil to cover that 2" opening. Then carefully insert into bottom grate. With the hinge open I then loosely stuff some alum foil at the side openings to block those as well.


MES MASTERBUILT ELECTRIC SMOKEHOUSE
I now smoke with a real smoker, and don't have to fight temps.... A lot less work...

