It's known that Spine can't do a normal 360° and so it's become standard to do 3x 120° key frames. This is problematic when attempting a tween ease, as most people defer to copy/pasting the rotation and moving the key frames closer rather than painstakingly figuring out the actual rotations per frame. It's not ideal when looking for accuracy and can easily fall apart visually. After some tinkering, I came up with a great hack that solves this and am offering a solution on implementation into spine for any devs reading this.
Essentially the trick is to create a standard 0-120 degree rotation on a bone, then copy that bone and parent it inside the first one. Repeat this as needed, as every 3 produces a full 360° rotation. Now select all those key frames and apply the same ease as needed. This is extremely useful for creating effects like a wheel spinning up slow to fast to slow again.
My one issue with this is it's very cluttery, as something like a 1080° spin uses 9 nested bones. Since true rotations with easable control is a highly requested feature, I've thought of how this working hack can be implemented into an update:
Create a new bone sub type (we'll call it multi-bone). Basically it functions exactly like a bone in the skeleton except whatever is done to it can have its effects "multiplied" (EX: multiply [3] times). In essence all it will do is duplicate itself X amount of times in a series of parent bones under the hood, but in the skeleton UI it will be one easy to manage element.