Literally the fish can be anywhere, yes - the downward positions can start to produce the fish, but still expect them to be upwind feeding on terrestrials.
If you have just come off the boats then you should, assuming all has gone as planned, have a good idea as to where the fish are showing. Just like during April, the spurs are the place to head towards. I expect to always be fishing a floater and if the fish are more than a couple of feet down, then I am very surprised.
Care should be taken when wading.
Wading in my book does not come recommended. It scares the fish out, and the fish can really come in very close during the later stages of the season, and more to the point it can become dangerous. Low water levels can mean it is possible to wade out into very soft mud. And get stuck. If you are alone you could well be stuck there for a very long time indeed. So if you do get your feet wet then take great care.
There are a few methods I use in September, unlike during the last three months our approach has become streamlined (liked the fish).
Dries. Yes, yet again these surface flies will produce fish when nothing else will have quite the same effect on you, or your basket. Floating fry can be great, especially in the mornings. Daddy long legs and, to a lesser extent, wasps, appear on the surface and are taken by the trout. Often daddies are best fished wet, but more of that later. Shipman's always produces fish as too will suspenders.
Nymphs. I will use nymphs during September, but very rarely since I feel that they fish too deep.
Wets. Fish near the surface, try the same flies as for the min-muddler technique in a boat.
Lures. White lures (appetiser) can be good, but black lures can be absolutely amazing. Fish very slowly.
An effective method is to fish Shipman's, daddy, and black lure all on the same cast. The drop allows the dries to fish as such and then fish wet as you retrieve. For some reason daddies work far better fished as wet flies. They take many good fish for me each and every September.
Early afternoons have a tendency to be best during September. Make the most of the fishing, unless you travel, it's got to last you through the close season.