I grew up in Colorado. They used the old fashioned mechanical voting machines. I don’t think anyone counted by hand.
Any voting machine or counting machine can be manipulated and it doesn't have to be done by the election personal. The old punch card ballots in Florida that gave us hanging chads were very easily manipulated. Scantron type counters can also be manipulated very easily, of course the final stage is when totals are reported to a central accumulation point there a very few crooks can manipulate the totals.
If precincts were made smaller and ballots were hand counted the possibility for fraud would be vastly reduced and that is a fact. The use of computers for tabulation makes stolen elections inevitable, the delay in getting counts from large cities dominated by democrats allow them ample time to create votes as necessary to effect the outcome.