Hello, this is just right up my alley... check some of my pics, I have turned a pen and a bottle stopper. You really need stiff "raw" leather to make it work well and using thin CA to bond deep into the fibers. Using soft leather can work, but I would only suggest it if it is layered between thicker leather. I have done both soft and stiff leather. Softer leather will take more time and also it has been split. In thinking that soft would be better, but the fibers are then more dissaray having been split.
I get my leather from work. I work for
www.wescoboots.com and we use stiff full grain leather for our Insoles and Midsole materials. I do not suggest using older belts. Since belts tend to absorb sweat/salts and most belts are not full grain, rather thin layers stitched together. With Full grain leather "raw", this is leather that has been processed upto the point of just before adding softners and dyes. Leathers at before this point are 1 of 2, Salted or Chrome. Its like a preservative, plus leather has formaldahyde in it aswell.
Since I like working with the raw leather, I feel I have more control over it and how to color or finish it. But it will be ones preference to try out and see what works best.
Good Luck post pics. if you have anymore question you are welcome to PM. MAybe work something out to get you some samples of what I use.
Ray