Starting with 1/4" cork underlay , a few cork rings , and some craft foam , assemble and glue all the pieces on a 1/4" Mandrel. (in this case I used a piece of 1/4" all thread).
Once the glue has dried, use a wood rasp to get as close to a round shape as possible.
After that it's time to use the lathe (homemade or whatever) and start sanding with 80 grit to get everything round and uniform.
Once round, it's time to use a finer grade of paper 120 grit and start your priliminary shaping.
Keeping an eye on what shape you want to acheive start working the areas that need to conform. When you have achieved the basic shape and get fairly close to the final shape , it's time to switch to an even finer grade of paper 400 grit. If you want a silky smooth finish switch to 600 grit afterward. ..........below is a pictorial of a full wells grip from start to finish. Composite sands almost the same as regular cork. If you substitue Burl cork be aware that it is harder to sand , so you have to take caution to sand everything uniformly.
Experiment/ use imagination/ and most of all have fun!