The honest prerequisite is a list of people who already know you, or a partner willing to invite theirs. Registration comes from somewhere, and for a new business that somewhere is usually an email list, an existing customer base, or somebody else's audience. If you have none of those, the effort of preparing and running a session will produce a handful of attendees, most of whom you already know, and the hours would return more spent building the list first.
Where they work well is at the decision stage rather than the awareness stage. A session explaining how to choose between options in your category, or walking through something people find genuinely difficult, attracts people who are actively deciding and gives them an hour of your thinking. That is a much stronger position than any written material, because they hear how you reason and can ask questions, and the conversion rate from a live session is typically far higher than anything comparable.
The format details that matter are unglamorous. Keep it shorter than you think, because attention drops sharply past thirty minutes and the questions are frequently the most valuable part. Record it, because the recording will be watched by more people than attend live, and the registration list is valuable regardless of who turns up. And decide in advance what you want somebody to do afterward, because a session that ends with no next step wastes the attention it earned.
Consider the smaller version first. A short session for six people who have all asked you a related question does most of the same work, requires almost no promotion, and tells you whether the material holds an audience before you invest in the larger production. If it works with six, it will work with sixty.
Whatever the size, follow up individually rather than only with a group email. The people who attended live gave you an hour of their attention, which is far more than almost any other marketing produces, and a short personal message referencing something they asked converts at a rate no automated sequence approaches. That follow up is where the value of the session is actually realised, and it is the step most often skipped in favour of preparing the next one.