At brazil at 2014 election (second round with only shills candidates, they rigged the re-election of an candidate and other shill allowed it), it was something like that:
1-You counted some amount of votes and allowed the vote count to run normaly
2-Check if candidate A has less votes than B, if yes, at the next batch of X votes, all votes not for B goes to B. If not the votes works normaly
At brazil at 2014 election (second round with only shills candidates, they rigged the re-election of an candidate and other shill allowed it), it was something like that:
1-You counted some amount of votes and allowed the vote count to run normaly
2-Check if candidate A has less votes than B, if yes, at the next batch of X votes, all votes not for B goes to B. If not the votes works normaly
3-Count the next batch of X votes normaly
4-Go back to 2.