No flush? Bad seeds? Bad lighting? Bad trimming? you need to give us a bit more information before you can get a real answer. If you didn't cure your plants, just drying them till they were crispy, then your answer is probably there.
If you're using chemical nutrients and not organic and it tastes like crap you gotta flush that shit out if it's tasting bad -- or better switch to organic then it always tastes awesome and you don't have to flush. If it's grassy/planty you're not drying/curing properly.
When you say stank you'll have to be more specific. A lot of strains (including some good ones) can have a sour smell that can range from diesel-like to rotting fruit to even urine smelling (super silver haze smelled like cat piss to me). Sensi star for me was like pungent old gym socks. A real stinker, but good stuff. I prefer strains that aren't too stinky. Of course there are some skunks that smell like.... well.