It's helpful if you put a grid on both tube sheets, similar to a game of "Battleship". You would also want to measure the distances from the corresponding holes to cut the flues to match the length. If two guys are doing the job, the bottom row can be lined up by using a piece of bar stock or something similar to line the flue into the hole off the barrel bottom. Once the bottom row is in you can just keep sliding the remaining tubes on the lower ones.
Superheater tubes usually require a couple guys to safely lift but are easier to install once the smaller flues are in place.
John Hillier