I am involved in marshal's training (for non-rally events) and have never considered the need to train marshals in crowd management. The number of incidents involving cars breaching the barriers is very low and I have always found that the marshals at the scene just get on with it. We shouldn't get hung up on or beat ourselves up over an incident with extraordinary circumstances that made things very difficult to deal with.
The scene of a serious accident is inherently unsafe and bystanders should be kept at least 10m away, leaking fuel (and there is always some of that) indicates that the cordon should really be at least 20m in my opinion. Tarpaulins and blankets are useful as screens but if people want to film they will, albeit now from 20m away. That said I did once have to ask that an airship was moved!!
I have always found that the venue staff are very good at managing the public and many disappear when asked to provide their details for the Police as potential witnesses!
