But I still don't understand how Rand could weave Saidar without being able to see the flows. I had the thought that since linking and using an adam create a similar scenario, that perhaps it's still Nynaeve's ability with the flows that makes them work, the same way a Damane is doing the actual channeling but the flows must pass through the suldam first. But, to my knowledge, Nynaeve didn't know exactly what she would need to channel, since Rand sort of just experimented with the weave.

But when channelers link the person in control of the circle can draw on either side of the source. And they can see it as well. They can draw on all five powers of both and interweave them if they would like. A little saidin and a little saidar.
I don't think you can sense the opposite power wielded by anyone outside the circle though. Daighan didn't know arangar was holding saidin until her ashaman yelled that she was channeling even though at the time she was capable of throwing a literal mountain of saidin at whatever she wanted.