If you do the math, in our precinct we have about 40 seconds to process each vote. Time polls are open/ number of registered voters. This means no step in the process can take longer. We can improve the throughput by adding voter booths so voters can take several minutes to do a complicated ballot, but the bottlenecks remain at the check in table and the ballot counter. So how is it we are slammed all day to handle a 65% turnout, but the inner city precincts can handle 100% turnout no problem? I suspect a shortcut....
In my county, more than 50% of the votes are absentee or early ballots. It has been that way for quite some time. Ballot verification is done by county and city employees, supplemented by paid temporary staff. The temps are hired from referrals provide from the Democrat and Republican parties.
The voting period is about 30 days long, which is a bit too much for a typical volunteer. There are unpaid volunteers acting as poll watchers on election day, and volunteer (but paid) election judges from each party on election day. However, election day often receives a minority of the votes counted.
The State permits last-minute registration and voting with a minimal display of identification and evidence of residency. A utility bill may be accepted in both categories.
There are also provisional ballots available to anyone who will sign an affidavit. Provisional ballots do not get counted unless an election result is contested.
Last-minute voters have historically been less than 0.5% of the vote. In my experience they are almost always Democrats.