This first exercise as you explain it is what I call: become horse with the horses.
Parelli gives a little hint on this sort of exercise in his dvd, where you should be with the horse for half an hour or so and do nothing.
But I interpreted that as a constant way of hanging about with them and doing my own thing in the meantime. Whereby I would stop in between to give hugs or a little scratch to the one that stayed near me. I could read a book (they would come to see what I was reading) or even doing some work on the laptop (beats working in a boring office...). But the best way is when I started to pick up the droppings daily in order to prevent worm spreading. This is a very good exercise to keep you busy and be with your herd at the same time.
I only had to watch them coming near the wheelbarrow to inspect what's in it, especially when it is very full... as they like to fling it over so you can start all over again, the villains!
I agree with Susan on the handgiven treats.
It depends not only on the horse and the human, but even on either one's mood of that day/moment.
Tachat will not be bothered too much about treats, if he's not in the mood you can forget about it!
Wodan would come over to earn some as soon as he sees something could be received...
My Billy is very mouthy so with him I have to be very careful on the treats or they become a threat... to me!
Since I started with clicker training recently, this was one of the first issues.
I was acting quite like you suggest in the first exercise, while picking up the droppings taking an interval when one of the horses came to 'check' on me
But the problem was that the others than quickly noticed that he got a treat, so they also wanted one and I got surrounded by horses all wanting something from me: treats.
My trainer suggested therefore to separate the horse I would like to work with from the others, so at least we were left in peace and could concentrate on each other. I will try that but somehow I feel a little sorry about that because before it was really the 'natural' way...