Never smoked a chicken so it's all new to me.
Have to agree 100% on the brine. We have done several smoked turkeys for Thanksgiving. Brine is a huge help. I use a Home Depot 5 gallon bucket to brine birds. Of course treat yourself to a brand new one and wash it well. You could toss a couple 8 pound chickens in one. Plenty of room for more than one in the 40" MES, so no need to leave empty space.
4-5 hours seems good for time, but definitely trust the thermometer over the clock.
My understanding is that it won't, which is why I haven't smoked one in my MES yet. I don't want to smoke and then have to finish on a grill or in the oven so I guess I'll have to break down and try one solely for the meat - knowing the skin will be rubbery and have to be removed....
Good luck, it isn't too hard to get a nice result even if it isn't perfect. On my first try I had a brined spatchcock in a Weber and I happened to stumble on just the right amount of fuel and heat. The bird had a golden finish just as the fire ran out. It made a good presentation for a family dinner.
The 40*F to 140*F in 4hrs. safety rule can get you to cold smoke chicken for 2+ hrs. to have them finished in 4hrs. Spatchcocking will open the bird up for more smoke contact since there is a shorter smoking time and finish them faster. Cold smoked with the AMNPS or AMNTS and BBQ'ed on the grill without heating two different smoker/grills. Cold smoked burgers for three hours then finished under 4 hrs. is good too.
I haven't smoke much chicken in my MES, but what I have smoked, I skinned the chicken first. Unless the skin is fried extra-extra crispy in a skillet, I don't like nor eat the skin, thus I peel it off to start.
Shop n' Save has chxn leg quarters at $.28/lb. I don't even think about my MES when it comes to chxn, only my grill. Fill the 12" AMNTS then smoke 'em on the grill without heat for 2 hrs. then build a fire and BBQ 'em for 1.2hrs., done in 3.5hrs.total time with skin on to keep 'em juicy. Eating the skin is optional. I heavily season the underside without the skin.
Both hickory and apple are very popular for chicken and other poultry and for pork as well. How strong a smoky taste do you want? Hickory is super strong and you really only want to use it for a couple of hours at the most with chicken--depending on how long you'll be smoking it. Apple has a lighter and fruitier smoke flavor and can be used for the entire smoke. You can't go wrong with either one and...nothing wrong with mixing the two. I mix wood pellets all the time when I'm trying to achieve a complex but complementary smoke flavor profile.
Any instructions telling you to rinse the bird are outdated and wrong. The updated thinking is that more harmful bacteria is spread among the bird and into the sink by rinsing off the bird. Don't bother to rinse. Paper towel the outside and then apply your dry rub. Also, skip the pouring two cups of apple juice into a drip pan. In the MES that would be the water pan. Filling the water pan with liquid won't keep the bird moist--it'll steam cook it. The MES is so insulated that just about any meat smoked inside it comes out moist. That's been my experience over the past three years. I leave the water pan empty and foiled over. The turkey breast I smoked turned out really good and it had been my first time smoking one.
The recipe you linked to advises smoking the chicken an hour per pound--depending on the cooking temp, of course. An 8-pound chicken should therefore cook for about 8 hours or until it hits 165° IT. I'd say if you go with hickory smoke it for about 3 hours before you pull the AMNPS out--only you like really smoky meat. Last week I smoked two boneless chuck roasts over a combo of hickory and Pitmaster's Choice, which is a mix of hickory, maple and cherry woods. I smoked them for 5 hours over the pellets and for 9 hours total. To my wife and I both roasts were oversmoked but that could be due to the way those beef roasts absorbed smoke. I've smoked pork ribs over hickory pellets for about the same amount of time which tasted perfectly smoked. Same thing with some pulled pork I smoked 2 weeks ago.
Eight pounds is a nice size bird but I smoked a larger turkey breast in my MES 30. The primary thing to keep an eye on is the internal temp. You want the IT above 140° within 4 hours. It's pretty easy to accomplish that with a whole chicken. My favorite smoking temp range is 235-250° but just about everyone here has their favorite temps for smoking in a MES.