what do you think about my bet here?

I think is better 3bet preflop.

Also, I don't like your bet on the flop.

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Agreed, but what size would you use?

My instinct here is usually something big like 15bb, to max on folds. Plus I think I can exploit postflop so I don't mind lower SPR. But thinking about it I can see the case for a more modest size like 12bb too.

Sizing 13-15bb will be fine OOP.

With two overs and a back door flush draw, you can float a flop cbet by button. No need to donk bet here. While donk betting can sometimes be a good play, thereÂ’s a reason itÂ’s called donk betting - it mostly is a bad play. Donking is most effective when calling from the BB on small dynamic flops. You will have more two pairs and straight draws than a PF raiser will on those flops. A donk bet prevents the raiser from checking back in these spots and taking a free card. This flop is T high and pretty static, not a great flop for a donk bet. In any case, donking is a fairly advanced strategy and you can easily crush 2NL without it. If you really must bluff on a flop like this then check raise. As others have mentioned, you really should be three betting pre - that would make a bluff far more effective as well. Your PF call has capped your range; you wonÂ’t have any premium hands here, and overpairs can be eliminated from your range after a call. If I were BTN I probably would have called, or even raised, depending on exactly what hand I had.

Plays like this can work at 2NL, as you found out. At higher levels a c/c or a c/r line will perform much better in spots like these.