Re: Practice casting
The leader is not that important when practicing your stroke, unless you will be using heavy flies and are not used to throwing them (on your 9wt for example). In that case, I would then use a regular leader matched to the fly you will be practicing with that you have cut the hook off of.
I usually practice with no heavier than an 8 wt, and just tie some yarn on the end of whatever leader is on the line already. But I am just casting to get exercise and work on techniques.
There are no special leaders for practicing with, unless you want to see how different tapers perform.