RK,
the terminology has changed a bit since the introduction of the new JSP. You describe the 3 jobs well, but the names of the jobs are as follows:
The Visiting Officer has the task that you describe as the Assisting Officer - who has the long term task of representing the RAF to the bereaved family. It is a long, difficult and emotional task and I have the utmost respect for anyone who does it.
The person you describe as the Visiting Officer is in fact the Informing or Kinforming Officer, whose task it is to take the initial contact with the next of kin to confirm the injury, capture or death of their loved on. As you rightly state, that person has a short initial contact and may often never have any dealings with the next of kin beyond that initial kinforming.
Training is available from the Padres for Kinforming officers - covering issues like do's and don'ts when dealing with bereaved people, what to expect etc. Bereavement courses at the Armed Forces Chaplaincy Centre are also available and are very worth applying to do.
Increasingly, Visiting Officer training is also becoming available on stns too, usually run by the scribblies and the padres in tandem - covering the admin issues the VO will need to help the next of kin and the "soft-skills" of dealing over a prolonged period with bereaved people.
Hope this helps to clear up any confusion over terminology.
Editted to correct errors in spelling - oops!