The Kayfun is no more difficult to coil than the RSST, and I would argue that the RSST may be slightly more difficult, though they are both very easy to do. The most important thing is to be able to check the resistance on the coil. Not sure why everyone thinks wrapping a wire around a wick (metal or otherwise) three or four times is an advanced application. It sounds much harder than it actually is, and a great deal of satisfaction comes from jumping in and doing this. A few key tools and measuring devices is all it takes, and the many YouTube Videos make it easy. And, if you do mess up a coil, it's only a few cents to try again. Of the RBA's, the Ithaka has been the most challenging, because of the marrying of resistance and non-resistanc wiring. You can get around that by buying "Ready Wires" and achieve pretty much whatever resistanced you like, quite easily. RBA's are not particularly difficult, and everyone I know has been able to do it just fine after an attempt or two. Knowing what you're doing, of course, is the hard part, that's where the videos come in.
My two cents. Good luck! Best to you!