There is a trick we use to cast a sink tip line. Once you learn & Master the technique you will be surprised at how easy it is to cast.
1) retrieve the line until you have only the sinking tip and a few feet of running line beyond the rod tip.
2) execute a roll cast, this will bring the line to the surface
3) immediately after the roll cast perform a single back cast before the line gets a chance to start sinking again
4) Haul & shoot, (you should be able to cast the whole line or very close to it)
The man who coined the phrase "Money can't buy happiness", never bought himself a good fly rod!