Back in the 90's I helped put on a training classes on the new "shear wall requirements" of the 94 UBC. Found I could get ICBO, now ICC, to come in and provide all sorts of classes. Those cost money. So we went with a combo of suppliers that were willing to come in for free. The two that came in were APA and Simpson for details on shear walls and connections and paid for one ICBO class to make it a two day training event. Somehow we got 80 plus contractor, designers and building inspectors, reviewers and officals. Most stayed for the second day.
Bottom line was get those you know will come (BO's) and invite the contractors, designers and others.
Short addition to the story was we have enough funds to start yearly classes after that. Then we would really bring in the ICBO speakers and pay their free and reduce the cost so people would come to the seminars.