Here is a link to elk nuts calls
http://stores.elknut.com/Categories.bok?category=Elk+Calls+and+Mouth+Reeds These work very well and I also like the primos ultra thin cow diaphragm.
I would just get single and double reeds.I like to sound just a bit smaller than the bull I'm after
Get yourself a bugle tube with an expansion chamber on the end "chuckler"(elk nuts).these tubes make very life like calls and give you many different sounds.
practice and you will be able to make elk sounds like a pro.
For locating bulls you can use any bugle "BUT" when you are in close (under 100yrds) and need to mimic the exact sounds,intensity,chuckles of the bull your after I have found the above setup to consistently fool the elk.When you do get a bull interested and he does start to come your way,as others have said less is more.You are basically trying to call as little as possible while still maintaining his curiosity.
When a bull hears you they have the uncanny ability to pinpoint exactly the spot you are standing on,I very rarely bugle right back in the elks direction with close bulls.I throw calls to the side and behind me trying to throw off my location.
Bugle very sparingly while throwing in various cow sounds and you will be on your way.