You can serve as a shadow union organizer, provide organization and a plan for warehouse workers. Study what the Teamsters did
https://teamster.org/content/first-teamsters-building-union
1. Organize offsite meetings for influential warehouse workers, convince them to become local union reps for each warehouse
2. Those leaders recruit lower level members to join the union and pay part of their wages into a fund used to recruit more union members and hire outside leadership (lawyers, others experienced in forming unions)
3. Quickly grow your membership while building a war chest but not actually hurting operations
4. Organize a strike that actually stops the ability for more than one critical facility to ship and receive products
5. Block access to the facility for any scabs or temporary workers that the company hires
6. Be ready and willing to negotiate with management, understand what you actually want.