There’s no special way to communicate recommendations. It can be done any way the committee chooses. Right now the medium with the lowest latency is the meeting notes of the PC here in the Cardano forum. So yep, since the recommendation was communicated, step 3 is done.
What you’ve mentioned about a special technical document is (as I understand the process) in step 5, and here the signing authorities may request more info from relevant members of the Parameter Committee in creating the formal change request that can be referenced for the change.
But I don’t want to preface this all too much here because it is a new process, which I’m describing informally, and when steps 4 and 5 area ready, they will be made public. I don’t know for sure where the communication will come from yet, but I’m sure it will be amplified widely.