It didn't take long. Dalmatians are very intelligent and learn quickly.
I started working with him at the end of last summer's corn season (sep), then "tested" him this year when the farm stand opened in July, and he remembered from last summer (just needed a little "tweaking").
His first instinct is to try to bite the whole thing, but I taught him to take small bites with his front teeth to remove the corn from the cob. He picked up real fast (because there is food reward involved)...