When I am fishing indicators I use basically 2 types.
I really like thingamabobbers for fishing large flys in moving water or choppy water. The larger ones are great at suspending the flys and they never become water-logged. They work well when the distance between the flys and the indicator are shorter than the lenght of the rod you are using. (Which is also another good reason for using longer rods) They are very good for most fishing situations.
I also use Twist-On strike indicators (called Turn-On). They are my go to strike indicator when I am using long leaders especially anything longer than 12'. You can place the indicator at the desired spot above the flys. I usually only use 1 1/2 twists of the indicator for this application. When you get a fish on you strip the line in until the indicator is at the rod tip. Then strip the line quickly and the indicator will slip down the leader, making it much easier to land the fish. They are also a bit more stealthy when fishing for heavily pressured fish.
You can also use another trick with twist-on's that is very helpful. Use 2 twist-on indicators. By using 2 indicators you will know exactly how your flys are drifting as the 2 indicators will point in the direction of your flys and allow more accurate drag-free drifts. The use of 2 indicators is not recommended when you are fishing with very long leaders and want to strip-slip the indicators down the leader as they tend to jam against each other.
Jimbo