They have it down to a science.
Once they calculate their cheating margins, they simply go into a backroom with their dirty voter rolls and start filling out ballots on behalf of people who didn't show up.
Often when they are pressed for time and can't fill out all the candidates and races, we get these impossible occurrences like more votes for the state controller than governor etc.
In 2020, after they stopped counting, they really went for it dumping MILLIONS of fake Biden-only ballots, rescanning multiple batches etc., because the Trump landslide was that massive!
"Elections are RIGGED!"