I've mostly been working with pearl cotton, which is pretty strong even at 20/2, and haven't had problems keeping the shed open as much as when I was using "fuzzier" threads. (I tended to employ the "use my fingers to ensure the shed is open" technique)
One technique I've not seen mentioned is "un-weaving" when you find a mistake. I know it's a pain, but I'd much rather un-weave a few (or quite a few) rows and try again rather than have all that work go 'to waste' because the band looks bad with all the mistakes. The person who taught me the basics of weaving told me to just "skip an inch of warp and start again" if I messed up, rather than un-weave to fix it. I soon learned that I'd never have a piece over 4" if I followed THAT advice. Not in the early days, at least. Necessity forced me to learn how to unweave, and, thankfully, I've gotten pretty good (and fast) at it. Good luck!
