Every place that participates would need their critical industries to be unionized already with a non-corporate captured union. They would then need to get in contact with global union organizing groups, like the IWW or IWA-AIT, the first of which is a global union, and the latter is an organization that can help coordinate the radical unions willing to commit to a general strike.

However, it will be up to the people who form the grassroots unions in each country to push coordinating with those groups to develop a global plan, and it will take some time for that to build up enough to be viable. Though we are also rapidly running out of time to prevent domino effects from happening due to climate change, so we really need to get this happening double time.