Couple of things:
Rattle bags are fine, but the problem is volume. The Knight and Hale Pack Rack is VERY loud and, IMO - more realistic than a rattle pack. I thought it was another gimmick, but I think its louder than hitting real horns together. Easier too. Can put them in my waist pack and walk around.
Play the wind. You must play the wind. Bucks will move downwind of the sound so they can use sight and scent to figure out whats happening. This means you need to put your back to the wind, face down wind. It helps to be in camo or in brush.
Mature bucks are tough to fool. I've been up in a saddle rattling to a mesquite flat, watched big mature bucks haul tail towards the sound, then stop at the edge. What are they looking for? The fight. They want to see it. If they don't, they know something is up and will often turn around and retreat back to the brush. I've never used a decoy to solve this problem, but it could be done.
How long to rattle? Loud, intense bursts for about 10-15 seconds. If you've ever seen a buck fight, they get after, stop, get after it, repeat. You could go longer than 15 seconds and be fine, but I've never seen a buck fight with constant noise for an extended period of time. Often they are locked up and its quiet, or they are walking around each other waiting to get after it again.
If you are on the ground, it wouldn't hurt to hit some brush, use your feet to make noise in the grass, etc. At least initially. It can bring more reality to the situation. Stop your movement after a while so you don't give away your position.
I also think you need a decent buck population in the area to make this work. Low deer or buck density means there just isn't much buck fighting going on, and that noise means nothing to the bucks within ear shot.
All my opinion from what I've seen and done. I've seen it go against these rules too. Have rattled some real big dogs up that I could have shot with a bow from the deer stand. Just depends how much they want the fight more than anything else.