Could start with topology. I first drew some of what I look for when modeling something like that, with as less vertices as possible.
Usually I would examine much more references but I only looked at pic you linked in this one.
Would probably do the bulging part on top of the thumb rest differently than what I did here because It’s more prominent. And also add more geometry to get rid of the 6-sided pole.
From top left:
- a perfect circle has vertices evenly spaced around the perimeter. I drew some cuts where I absolutely need them and then cut the rest of the wheel circle evenly. I placed poles on the key areas where I would be turning the face loops
- some more key cuts
- here you see what the poles do. there is a continuous face loop around the wheel and the edge loops from the inside parts gets sent on the wheel inside, instead of across where they would destroy the perfect circular shape
- there is a defining edge that needs to be outlined. should’ve outlined this earlier but should work
-> Can start with a mesh circle that has 20 vertices
Wouldn’t normally model like this but I quickly did a mockup in Blender without reference image and used only those lines to guide where the vertices go.
Not a pretty sight but works as an example I guess.