Work backwards from the date the U.S. property needs the system running. Documenting the proprietary knowledge is the long pole and should start first; corporate and payroll checks run alongside it, and drafting comes last.
Sequence the evidence, then the drafting, then the filing
A realistic order is straightforward. In the first weeks, verify the corporate relationship and pull payroll proving the qualifying year, because a failure there ends the plan cheaply. In the same period, begin gathering the internal documentation of the system, which is slow because it involves people who are also running a business.
Only when both are in hand should the petition and support letter be drafted, so that the description matches the evidence rather than the other way round. After filing, allow for standard USCIS processing, or premium processing where the employer elects it, and allow further time for a possible request for evidence. If the property opens on a fixed date, the honest planning assumption is that the filing should be complete well before, not immediately before.