arphaxad12 > Was surprised that you dug up this thread to ask those questions on organised shoots on CS. :sweatsm:
Over the past 1 year, I did have the chance to attend several of the advertised shoots so here's just my humble opinion.
For group shoots be it indoors or outdoors, one between 50-85mm should work well for most people to capture full body shots as well as closeups.
I use the 85 for at least 80% of my work and other times a 35 or 200 when I wish to have a change in perspective and there is sufficient distance to use them.
Having a lens with aperture of at least 2.8 will help to throw the background off focus and draws the attention of your viewer to your subject in the picture.
The use of which lens is highly subjective and to your creativity. As mentioned in other sections of the forum, there is no particular fixed lens for portraiture usage. What works for others might not be for you.
On reflectors/wind machines/lights,
Have a look on which ones that did state in their posts. That will be provided.
For those shoots with large groups of participants, such equipment are not likely to be provided as it is impossible for the organiser to have so many to be given to each group.