Howdy,Jay.I'm no expert ,but have been the "grunt" for several over the years.
First ,the fine cooks above have touched on many of the tips for doing comps/caters,etc.I won't even try to add to them.
The cooks that tried to make me smarter always say"you wind up with what you start out with.Now,when some of these old cooks here were starting, Jimmy Carter decided to help the ranchers and made the beef triangle about 75% choice.Thus, you could get an upper choice CAB,or a bottom choice from a 20 year old dairy cow.[which should have gone into the "burger barrel"
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Since,I hated to waste $12-$15 on a 16-18 lb packer,I wanted to research it perfectly.
After I researched it until I got ulcers and ask every question of the "big boys",they would finally say"why don't you go cook something.Make an adjustment and take good notes,and after about 5-6 decent packers you get one you can eat most of."[Yes,we learned that the basic CS, developed over a half century ago,would leave even our mistakes edible
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You mention fat up,or down and the "big boys"always say"go cook something and worry about that later"[guess maybe it depended on the cooker?].I'd ask about how much trimmin' and I'd get the same answer.
Now,as far as temp probes,these old cooks around here never heard of them-much less one connected to the cooker.They couldn't figure out where to place one, when cookin' a couple cases of packers.
Now,some say"don't open the door-or it will add 1/2 hr to the cook time". So?
Until you gain that experience/feel that is about the only way to learn.
Talking about placement of a probe,that is why some folks stick the Thermapen in several places,while they got the door open.That temp is just giving you a hint when to start paying attention.
Until you gain the experience/feel of
cooking several,you have to experiment.Since them old cooks around here didn't have a thermometer,running the skewer down thru top and out the bottom of all them flats was a good indication of"goes thru like butter".
Now,when them old cooks had a large cooker with a couple cases on and no skewer,seems like they always had a long handled two tined meat fork.When they reached across to the next packer,ran the fork thru it to lift it off and it slid off the fork,it was ready to toss in the big "holding cooler/hot box".
When all those packers set in the hot box a few hrs,until serving time,that would be what we call "foiling/holding,etc".
Sorry,I can't give you the perfect answer,but I think all the "big boys" were trying to teach me to K.I.S.S.
When I got a few under my belt,I'd know when to start using "tricks/tips".
Guess I better get off of here,before I get accused of makin' a "Smokin'Okie post".
Just my $0.02.