Button Reg raise 3x
Hero call BB w Jd9s

Flop 8d8c7d
Button cbet 2bb
Hero raise to 8.5bb
Button calls

Turn 4d
Pot = 24bb
Hero bets 8bb

Button call
River 8

So. What do we think about my turn sizing and then the river?

I think the turn sizing makes sense because it is a sizing I can use with some 8x and flushes. However, thinking about it now, maybe 8x might want to do a fair amount of checking because button will have alot of flushes themselves, and I do think I have way less 8x than the button here because he made it 3x preflop(I think I am folding A8o for example due to rake and facing a 3x sizing). Because of this, maybe my turn sizing should be sized more for the flush region of my range, and we could potentially size up to like half pot or more

When the 8 comes in, how do we determine our bluffs?

I think the best bluff might be something like KJdx that gets C/R on flop, because it blocks KK/JJ, and blocks the Diamond. Also a AdTx might be a good combination, however it is likely getting flat called mostly on flop, so it seems like Kd blockers are going to be used quite heavily.