Right, use the canning salt. I use kosher salt. You don't want the iodized stuff.
Canning salt is fine if that's what you have.
Important to note however that not all table salt is iodized
, so using table salt is also fine as long as the label says "...this salt does not contain iodide".
Morton's, Diamond Crystal, generic store brand...these all come in non iodized versions
Keeping that caveat in mind, table salt also works just fine if you buy the right type (if anything, the non-iodized ones seem to be more common).