Actually, from the description he was using a slop box or a commercially made tool called the Super-Taper. It applies mud to several feet of tape and you carry it around in a bucket strapped to your waist. This way many guys can apply tape at one time. It is a product of the Better Than Ever Tool Company in Canada. Sold here in the states at All-Wall.
Wetting tape is practiced where there is high temperatures, so the tape doesn't starve the mud for moisture. Some feel that this will provide a better bond as they dry out equally. I haven't seen an advantage.
The Super Taper system, described above, slightly wets the tape due to its operation as do wet and dry banjo's, the wet being more so.