One of the steps to acquiring a skill is to watch the professionals after you have tried it yourself. I did a quick search on youtube and found some...
Fill-in with kiln-fired bricks: https://www.youtube.com/watch?v=ju4Q62Lyxpo&feature=youtu.be Note the following: - no level, only the string - how the head joint is buttered - how many times he lays down the trowel - where the mortar board is placed - where the brick a placed - note the entire bed was already down before he starts Keep in mind this is fill-in, and not corners.
Fast fill-in with kiln-fired brick: https://www.youtube.com/watch?v=8VLlYiJobzY&feature=youtu.be So, to answer Marcin's question.... 800 bricks/hour
How to carry bricks: https://www.youtube.com/watch?v=1EF_8RQE4SU&feature=youtu.be I don't even know what to say to that.
Detail on concrete block: https://www.youtube.com/watch?v=Qfw679NHSAs&feature=youtu.be This explains some detail that we did not cover. Note how quickly the mortar is applied. What we were doing is something between the brick and block.