.25/.50 3 to a 4 flush river, first to act

[halpgr]

CO is a calling station. BTN seems pretty solid.

PokerStars 0.25/0.50 Hold'em (10 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

Preflop: Hero is UTG with 8[img]/images/graemlins/heart.gif[/img], 8[img]/images/graemlins/diamond.gif[/img].
Hero calls, <font color="#666666">4 folds</font>, MP3 calls, CO calls, <font color="#CC3333">Button raises</font>, <font color="#666666">2 folds</font>, Hero calls, MP3 calls, CO calls.

Flop: (9.40 SB) 7[img]/images/graemlins/club.gif[/img], 8[img]/images/graemlins/club.gif[/img], 4[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(4 players)</font>
Hero checks, MP3 checks, <font color="#CC3333">CO bets</font>, <font color="#CC3333">Button raises</font>, <font color="#CC3333">Hero 3-bets</font>, MP3 folds, CO calls, Button calls.

Turn: (9.20 BB) 2[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(3 players)</font>
<font color="#CC3333">Hero bets</font>, CO calls, Button calls.

River: (12.20 BB) Q[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(3 players)</font>
<font color="#CC3333">Hero ...</font>

I did some calculations. For the flush, with 4 random unseen cards. The chance none of them is a club is

36/45 * 35/44 * 34/43 * 33/42 = 39.5%. Thus there's a 60.5% chance someone has a flush.

I feel my set is probably good over a non-flush unless BTN has QQ. If CO has 65 I think he would be raising a lot more. So my equity is around 39%, less rake and the possibility of BTN having QQ. BTN could also have 99,TT,JJ,KK or AA here.

So it seems I have a thin value bet. So I'm thinking bet/fold is a good line for the river. A bluff raise 3 way would be pretty crazy to try as it will get called by a flush 100% of the time and a non-flush a lot of the time.

Check fold seems weak as I'm getting good odds to call and this is an obvious bluff opportunity.

Check call seems bad as hands I'm beating will not bet, but they may call as they called the turn. Hands that beat me will surely bet though.

What's a good line for the river here first to act.