Most likely test tubes with sterilized nutrient gel that contains the hormone. You'd need to surface-sterilize the stems too.
I wouldn't expect a high percentage of success (bacterial contaminations, weak/dead grape cells), so do something like 24 tubes to be safe. Look up the recommended hormone and nutrient mix for grapes. There's usually some research paper on these things.
There are probably people here that's done plants from cell culture. Listen to those people when they speak up. I'm only sharing my perspective from edible mushroom culture with some information I read on plant tissue culture.