my first instinct was raise to 500-600 in order to get the pot going. you're oop and there are a ton of scare cards (for everybody) looming. obviously it screams flush, but this guy isn't too good so who knows if he'll notice.

i really want to make a flat call work, but i can't pass up building the pot for a huge score.

If he has trouble getting away from hands then I think you absolutely have to bet out here on the turn. I mean, unless he's the sort who's going to keep betting once the flush hits (and not many are) I think the risk of both giving a free card AND losing value from a person who might call but not bet is too great to warrant a check here.

Given that, I think the check raise here screams how strong you are - especially with the all in. However, if you call and see the board pair on the river, you'll have to throw up a bit. I'm agreeing with everyone who says to make it $600. Don't let him see the river cheaply with two pair or a set here, you can't let him outdraw you AND have the price to do it.

Still, I think you should have led out $200 or so in the first place. Maybe you'll get lucky and he'll have A , or even AA and decide to see a river. Assuming it doesn't pair, with a pot of ~$1500, i'm betting $750 on the river hoping to induce a call from a big hand. Assuming it does pair... well, i'll check call a lot of bets.