First fix the corporate and payroll evidence, which is mechanical; then write the specialized-knowledge narrative with the technical staff, which takes iterations; then file, choosing premium processing if the U.S. project has a fixed start.
Do the slow creative work early and the paperwork in parallel
L-1B petitions stall for one of two reasons: the corporate documents are not ready, or the specialized-knowledge explanation is written by someone who does not understand the product. Solve both at once. Ask the accountant for share registers and a year of payroll on day one, and in the same week sit the specialist and her manager down to describe the proprietary process in plain terms, with examples of problems only she could solve.
Expect two or three drafts. Hypothetical example: a Boischatel building-automation contractor has a U.S. hospital project starting in January; the technical narrative should be settled by October, the file assembled in November, and premium processing purchased if the calendar leaves no slack.
After approval, a Canadian citizen applies for admission at the border. The initial period is up to three years, extendable to a five-year total, and any earlier L or H time counts, so tally it before filing.