Re: Dry presentation
As per your ? regarding a downstream presentation fishing a dry fly.
Work yourself into a good position upstream of where you can present the fly into the fishes feeding lane, put your cast just beyond the feeding lane, and upstream from the fish about 10', leave some slack at the end of your cast so you can gently raise your rod to drag the fly into the lane, now drop the rod tip and feed some slack from your line hand down stream along with the fly, when the fly drifts past the fish or the hole a safe amount as to not spook the fish, then gently pick the line up and recast doing the same thing.
This method is very effective using emergers also.
*Comments posted above are only my opinion. I may be right....eh, I'm probably wrong. Take 'em for what they're worth.*