Finishing a braided handle

[Carl513]

Hi everyone, 

I have been reading up in making whips. One author talked about applying saddle soap and then rolling it on the floor under foot or other object. The leather used on the handles had already been wet and stretched out before trimming down. 

My question is what function does adding the saddle soap do at this stage? Also, would it cause the leather to shrink more or help it set in place better?

Thanks for your time,

Carl