Hi again! No, at GCSE level, using a practitioner is not a requirement (The website states: "We recommend that students choose one or more genres or performance styles for their devised piece but this is not a mandatory requirement.") however I think it's easier because then you can justify your ideas rather than just saying "I thought it would be cool to do this" etc. In my school, we had to use the practitioner Brecht (Brecht is the opposite of Stanislavsky so you use a lot of gesture, gestus, chorus lines, direct address etc.) but there are other practitioners you can use such as Kneehigh theatre company, or Stanislavsky (naturalism). The exam board recommends using any of the following styles:
comedy
tragedy
melodrama
commedia dell’arte
naturalism
epic theatre
documentary theatre
physical theatre.
However they state that you do not have to follow these styles either.
For the devising log, you should mention ideas that you have specifically come up with as well as ideas you came up with as a team. Justify why you did certain things, but make sure to explain and evaluate your choices - don't just waste the whole word count listing everything you did during the devising process out! Use your notes from the lessons to evaluate different moments of your piece and choose what techniques you want to focus on.
When it comes to the actual devising itself, if you haven't already finished devising, I would recommend making a few plans. One of the things I did in GCSE was list a bunch of techniques I wanted to include that linked to my devising style and found ways to put them in my piece. Responding to the stimulus, we decided on an overall theme and meaning of our given stimulus and mapped out different subthemes and moments we wanted to explore. When working on each moment, we tried to include as many techniques as we could (without it being forced). This means you get much better marks as you will have an abundance of relevant techniques you can discuss in your devising log.