Can't speak for the Stilly but, the upper reaches of the Skagit and the Sauk are quite wade-able, weather permitting. Now as far as technique - oh the usual, you just carefully place one foot in front of the other in the general direction in which you wish to go :CLOWN
Old man who wishes he knew what to do with his wonderpole...
...and wishes he could get the smilies working!
The stilly is quite wadeable. The area up stream of Oso is the area to fish. Try the C-Post bridge, and Hazel. Hazel is the area where the river makes a bend right at the road, and there is a steep drop to a big pool. C-Post bridge is downstream a little, and is off C-Post Bridge Road.
The stilly is very manageable to wade, and just the right size for fly fishing. The Skagit and Sauk are bigger, and can be tough to wade much of. Fishing on those can be a case of driving from one big river feature to another, where the Stilly typically will have several pools and habitats available from one area.
There are several good places to fish the Skagit. The river is dropping fast which will open up a lot of the lower river to wade fishing. Your best bet is to stop in or call Skagit Anglers in Mt. Vernon for the best places to go. The phone number is (360) 336-3232. The address is 315-G Main Street, Mt. Vernon, WA 98273. I suggest dropping in to the store spend a couple of bucks on flies or something and then ask for info. Seems to improve the quaility of information when you spend some money in these fly shops prior to asking where to go. A few spots to ask about would be Lyman bar, Grandy Creek, or maybe the power lines. These places are not secret, you should be able to get directions to them.
The Sauk and the Skagit ahould both be fishable this weekend. The stilly takes longer to clear, but may have more hatchery fish above Oso. It's hard to give directions to the popular holes on the Sauk if you don't already know your way around. I agree about stopping in at Mt Vernon. All the pools recommended above for the Skagit are good; I might add the Jackman Creek riffle.
You want an 8-wght, a 10'-20' sink tip, and big marabou flies. Look for riffles with seams between fastish, (about as fast as you can walk) bumpy water and slower, smoother current. Quarter your casts downstream, and swing the fly slow and deep through the seam. If your satisfied with the swing, take a step and do it again. Keep going till you've covered the pool, head to tail-out. If you've got the space and time, if often doesn't hurt to try the pool again.