Smoking BBQ is all about slow cooking.
When first researching how to make BBQ (pre Internet days), information was hard to come by (hard to believe now, right!). However, persistence paid off when I came across Harold McGee's book 'On Food and Cooking'. This book, which is still quoted today and more-than worth the buy, gave detailed information about how collagen (the tough proteins that makes cheap cuts of meat tough)breaks down with heat. He went on to describe cooking meat at a low temperature, and all the benefits realized from this approach. Since meat can never exceed the temperature of the cooking environment, providing a cooking environment that does not exceed 145 deg F will, given enough time, provide meat at 145 deg F.
This is the basis of Sous Vide cooking! Brought to you by Harold McGee's book in 1984! I note that the French chef was credited with this approach in the 1970's, but McGee's book was my personal beginning on slow cooking.