Vinegar soak fixed my streaky float marks.

Claire's point about the mix ratio being the most important thing is where I have to disagree. In my experience, a bad rinse will ruin a perfect mix every time. The mix leaves the film, but the rinse water is what dries and causes the actual spots you see. If your rinse water has minerals, it doesn't matter how fast you dry it, you're just baking those in. A final rinse with distilled water changed everything for me.