I've tried about a half dozen different methods of treating rattan sticks. For me personally, the most important thing is to select the densest rattan possible when buying. Finding good rattan is, in my experience, more important than how you treat it.
I eventually tired of all the time-consuming treatment procedures. Since cutting your own sticks is pretty cheap, I now try to keep the work to a minimum and often use them raw. At most, I might take some heavy-duty fabric rigger's tape (like duct tape on steroids!) and wrap them tightly to slow the splitting and protect my hands from splinters. Otherwise, just get the densest rattan you can locate and replace as needed.
DPD.