Part: Part Six - Betting After the Flop

Completing the story

Turn
Heads-upPot 3,000 (15 BB)Q♦7♣3♠2♥COA♥K♥● 25,000 (125 BB)YOUmissed, but a scare card loomsBB● 25,000 (125 BB)Big blindcalled the flop, checksD

You opened, c-bet a Q♦ 7♣ 3♠ flop with A♥K♥, and the big blind called. Turn 2♥ - you pick up a flush draw to go with two overcards. He checks.

You have overcards plus a flush draw and the betting lead. Best?

WhyBarrel again. You have a heap of equity (flush draw plus two overcards) and continued credibility, so betting both pressures him and can win when you hit. This sets up a believable river bluff if you miss.
What happensYou bet 1,800; he calls.  Pot: 6,600 (33 BB).
River
Heads-upPot 6,600 (33 BB)Q♦7♣3♠2♥K♠COA♥K♥● 25,000 (125 BB)YOUmissed - but a scare card hitsBB● 25,000 (125 BB)Big blindchecksD

River K♠ - you actually pair, but consider the bluff line: this is a card that completes a story of strength and scares his medium hands. He checks.

A king arrives - a credible scare card - and he checks. Best?

WhyBet. The king is a card you'd often hold after three streets of aggression, so it's exactly where a triple-barrel is most believable - and here it also made you top pair, top kicker, so you're betting for value with the bluffs you'd also be representing. A coherent three-street story plus a real hand is the best of both.
What happensYou bet 4,000; he folds a worse queen.  The story (and the pair) win it.
You built a believable three-street story, barreling cards that favored your range, and the river king let you bet as both a bluff-representation and for genuine value. Triple-barrels work when the story is consistent.

A triple-barrel works when the run-out tells a consistent story - keep firing cards that favor your range, ideally with equity to back it up.