The therm probe is not a highly required piece of technical equipment .
A cook doing 50 packers,may go down the row with his two tined meat fork.
If he pokes it and it falls easily off the fork,he probably is satisfied.
If it hangs on the fork ,and won't release,come back in an hour and poke it again.
Like Smokin' repeats endlessly,take good notes that are useful to you.
This allows us to repeat our successes,or adjust our next try.
Smokin' also stresses the personal experience of cooking several,to know what it feels like,the next time.
We all would like to know the perfect feel,touch,temp,pull,resistance,etc., for the first time we cook something, that we might feel is costly,or time consuming.
It ain't going to happen,but it gives us the pleasure of cooking several,and eating still usually good meals.
Hope this helps a little.