You need to cut grooves where the cracks are to make room for working the product in deep. Cutting the grooves also gives you a clean surface for the product to adhere to.
As far as what to look for in a product, you want something that has good adhesion quality, and is similar in hardness to what the steering wheel is made of. If it is too hard, it is difficult to sand into shape without gouging away steering wheel material.
I tried JB weld two-part putty, but it was too hard, and cracked in several places where it contacted the steering wheel material.
So it failed in both categories.
Carl
