I don't have the Tsunami specifically so there is a reasonable chance someone might produce an answer a bit more specific than I can come up with, however since there are no replies I shall venture out a couple of fairly generic points that are hopefully useful.
Firstly the 'tsss' sound is likely because the heat retained in the wire after you have let go the button still vaporising liquid. I personally would generally expect a bit of that on a 24g build particularly with a few wraps, the more metal you have typically the longer it is going to take to warm up and cool down.
The dry hits I'd venture is probably one of wicking or hotspots. If it is wicking then it is probably due to being a little too tight in the coil, a little too tightly packed or possibly being constricted by the legs/the space it sits in. Wicking is a bit of a pain to get used to at first and there is not much in the way of helpful descriptions when starting out (beyond snug but not too snug). You do want to figure that spot out, in addition you also want to make sure that you fluf it out and tuck it in place, don't stuff it in there all bunched up or have it packed on the deck, just enough to sit loosely on the deck nice and fluffy. For hotspots you can glow the coil lightly and work them out (strumming over the coil with a flathead screwdriver normally does it well) or if your build choice prohibits that then go with a spaced coil.