Walnut shell is actually a pretty poor substrate for all manner of animals. It is completely non-absorbent, so it promotes bacterial growth. It can also be quite deadly if ingested.
I use newspaper for hatchlings and once they are feeding regularly and past quarantine I move them onto aspen Sani-chips. I buy these in bulk from the local monthly herp show for $15 for a big bag. It lasts forever... I buy it maybe once or twice a year.
I have also used shredded aspen and really liked that as well. It holds burrows a lot better than the sani chips, which my '06 corn really likes.
I use Care Fresh for my chinchilla and cavy, but not for corns... from what I have heard it is kind of a "humidity absorber." While corns don't need super humid conditions, they do need about 30-50% humidity... not super dry. I'd be careful there.
I would not use corn cob for corns because it tends to mold. I only use corn cob for my gerbils. They rarely urinate or drink, but the few times it has gotten wet (like when they back their litter up into the bottle) it has molded. Not a good situation for a snake.