Villain is running at 18/15.

Full Tilt No-Limit Hold'em, $0.50 BB (5 handed) Converter Tool from (Format: Bet The Pot)

SB ($80.45)
Hero ($50)
UTG ($183.80)
MP ($51.55)
Button ($51)

Preflop: Hero is BB with , .
UTG calls $0.50, 1 fold, Button raises to $2.25, 1 fold, Hero calls $1.75, UTG folds.

Flop: ($5.25) , , (2 players)
Hero checks, Button bets $3.5, Hero calls $3.50.

Turn: ($12.25) (2 players)
Hero checks, Button checks.

River: ($12.25) (2 players)
Hero checks, Button bets $8, Hero raises to $24

Feel like I'm getting folds from anything other than the flush, thoughts?

I may just lead out as a flush may fear a check behind from the button, Make it $10 -$12 and it accomplishes same thing.

You played it like a ton of people play their flushes. But a ton of people play their flushes like this because they get paid off pretty regularly.

I want a postflop read on this villain that he can lay down top pair type hands, not just his 18/15 preflop numbers, before I make a play like this.

TBH I think you're bluffing with the best hand here pretty often. An A or K would more than likely fire that turn. I imagine he'll fold a lot, but again, mostly because he'll rarely have a hand that beats yours... I'd probably just call it.

How often do you CR your big hands on the river?