I use floating line for nymphing. There are different ways of getting the flies down where you want them. How much weight depends on the weight of the flie and water conditions. I don't use a split shot, I use twistons. They come in a package like a match book. They are flat slim pieces of lead that you twist onto your line. You can pick them up at any fly fishing store. I like them because you don't need a tool to put them on your line and I guess your not suppose to bite split shot closed on your line anymore. (did that for years before I heard it was bad). The other thing that helps getting the fly down is usuing a weighted fly. You can use a big weighted Kaufman stonefly as a bottom fly and run a small fly above it. That is a great way to do it on the Deschutes. If you tie your own flies make up some weighted nymphs.
I'll look around and see if I have a diagram if not I'll take a picture of a set up. There are a couple of ways to do it. One is to take a piece of tippit aka (leader) and use a blood knot to tie it onto the end of your line. Leave a 8" to 10" tag line on the knot and tie the smaller nymph to it and the larger nymph to the end of your main line. The second method is to tie one fly on the end of the main line then with a piece of leader tie the second fly onto to the hook of the first fly. Both methods work. If anyone else out there has a diagram please feel free to post it.
I tie my dropper with a surgeons knot (basicly a double granny knot) about 18 inches about the weighted nymph and leave it about a foot long with an unweighted nymph (usually smaller) tied there. You can vary the lengths as needed, I fish mine with a floating line and a strike indicator. Although I have a new sinking tip I need to get wet soon.