Agree on the time for PMB, stud, jewelry and underwear check.
Last season my front row PMB was perhaps too long when I did it; I do stud checks almost always (not for sevens, obviously, nor at every game of a tournament).
I have become more observant as a referee, but as a coach also watch out for the self-safety issues of jewelry, not only with female players, nowadays.
As of this season checking for hard (field hockey-style) shin-guards as per Union directive.
Not once have I done an underwear check. Nor a Prince Albert check, for that matter.
To bring it back to communication skills: teams who I have refereed before tend to know that I not only am slow to whistle when there is potential advantage, but also will signal first aid to come on to the field while the ball is still live (as long as moving away from the injury). I'll call "injury" to make sure both sides know I am aware of it, of course, and will whistle as soon as there is any added danger.
Players accept missing say, a forward pass, if another player - even an opponent - is temporarily the focus of a ref's attention due to laying prone on the ground. Until the whistle is blown, their first priority as players remains to play - in attack or defence - but they all dread a serious injury to themselves, and would not wish it on other players. Hodie mihi, cras tibi and all that.