Turning Hands Into Bluffs

For a long time I'd believed (probably through misinterpretation) that bluffing when we already had some hand was not a good play. Often this is actually correct, but over the past few days I've seen several examples of situations when it is actually best to bluff despite having a hand that might win some percentage of showdowns.
If villain plays his hand in such a way that his range becomes transparent and we have any hand that fares poorly against that range; and if we have fold equity by betting or raising then we can turn our hand into a bluff.
The critical thing here is ranges and how our hand fares. Here's an example of a hand I played earlier:



Firstly, with the effective stack size I'm not sure the check min raise was sensible. But villain had been folding a ridiculous amount of the time to aggression post flop so I felt I could get tons of folds and if we call a shove I'd expect flush draws to be in his range so we're probably not doing too badly.
By the river due to my reads on villain and the way he played I was convinced that his range was a weak pair like a 9 with a bad kicker or a four. When the fourth spade comes - despite that we have a pair of fours - I just felt that I could get any nine to fold other than those with a spade in. So here we put villain on a range that we knew beat our hand but had an excellent situation to turn it into a bluff. I don't think I'd have even considered firing this river in the past. It may still be a negative EV play, but the very fact that I've started considering more options during play should make me a much more dangerous opponent.

Play Tonight
Won three games but ran really well. Every time we'd grown a good chip lead by the time the money was going in. All three players played very "fit or fold" post flop so aggression was winning pot after pot. In fact there were many spots where I think I should have been more aggressive but decided not to go over the top with it to preserve some fold equity. Pleased with that and once again I have 202 dollars so will try another $10.50 game at some point.