The HL should always have an idea where each LTG is in front of him. When it's anticipated as being close, our practice is for the covering wing to move towards his spot, rather than have the ball be tossed out to him.

Either approach, done correctly, will yield the same result, but going to the spot provides a more emphatic perception.

The wings, especially the LJ, usually go up with the down count.
They mark the spot with feet together, downfield foot is the spot.
Wings will come in for the spot, usually no closer than the numbers, but could come in further if it's close to the LTG or the GL. Of course if there are players in the way they have to stop. No dodging around and trying to re-establish your spot.
If there is a "close" call, the U takes the ball to the spotting wing and hands it to him to spot, throwing it to him only creates a chance he has to move off his spot to catch it, which would be bad.
I then decide if we measure or not.

On a close play on his side of the field, the wing should come in as far as he can without moving off his line; he should not be jumping over or going around players to get to the ball. If he can come all the way into the ball he should, but if he starts coming in and players get in his way, he should stop there.

If he couldn't get all the way in and a measurement is needed, the ball can be moved to his feet and measured from there.