We did that early on and the sticky stuff adhered to the pad and when we removed it some of his pad skin came with it. I don't recommend that. Go with the therapaws for padding and yes buy a second one to give him symmetry and to give him no choice but to use both feet for walking. He can't "fake" it by limping on the paw wearing the therapaw.
One of the theories out there about corns, besides the bacterial thing and thus treatment with Abreva, is that greys don't have as much padding in their, well, pads as "other" dogs. The corn is thus a result of rubbing inside their pad. If he's missing a toenail he MAY and I only say MAY be rubbing funny when he walks on that foot.
Corns suck! Some go away with treatment some never go away and you just maintain. Good luck.