Just a heads up on single hand spey casting - it's not easy! I only got into two handed spey casting this winter, and I'm already about as good as I am with the s/h rod, and I've been doing that for a couple years. In other words, IMO spey casts ar a lot easier with two hands than one.
That being said, if you already know how to do spey casts in an upstream and down stream wind, then it should not be a huge problem to transition to a s/h rod.
From my experience trying to s/h spey with a typical WFF line (mean more for overhead casts) is not easy. It seems that you end up stripping a fair bit of the thicker head past the rod tip, then when you go to shoot line after the change of direction cast, it does not shoot well until you get into the thin shooting line (duh). What I found worked for me was to do my change of direction cast, say a circle-c, then roll cast but do NOT try and shoot line as not much is going to shoot on this roll cast with part of the head still on your reel. I would let this inital roll cast unfurl but NOT hit the water. When it straightened out in the air I would do a back cast, shoot a bit of line, another backcast (or two) and once I was into my shooting line let-er fly! It would help if I knew how to double-haul, but I haven't learned that yet
It seems this would be easier with a shorter head (20 feet or so compared to the 37 feet on my rio outbound line) as you could strip the tip up to the head (not into the guides), change of direction cast, then on your roll casts let go and you are right into the shooting line and should get some decent distance.
Keep in mind I have not actually tried an Wulff Ambush style spey line on my s/h rod so I am pretty much talking out my a**
However with the short head on my spey rod I find after my roll cast the stripped in line SOARS.
If you have never tried spey casting I would HIGHLY reccomend a lesson. William Holmes does a s/h spey group class on the river (Vedder) for cheap like $50. Talk to Fred's or your local tackle shop.