Re: casting sinking lines
The sinking line can be a problem and takes some getting use to. Don't expect to cast it as well as a floating line. It is important that you get the line up to the surface before you start your back cast. It is important that the rod tip is close to the water before starting the rod tip moving on the back cast. One way to get everything moving is to coil line in your line hand as you strip it in so it doesn't sink into the water. When the fly is near the surface you can make a roll cast pickup. You do it like a roll cast but you aim the forward cast above the water and as it straightens out you start you back cast. You can feed line from your line hand and shoot what is left. This is not a long range cast. When holding the large coils in your line hand I lightly put my thumb over the coils so when you shoot the line it won't pile up at your first guide. It just takes practice. The above thoughts are using a sink tip line but will work with a full sinking line. Joni does a lot of this kind of fishing and may have some ideas for you.
It sounds to me that you would be better off with a sink tip line for this fishing. With a sink tip the line you strip onto the water is a floating line and you won't have the problem of it sinking. If you are fishing deep enough that a full sinking line is needed a striping basket is a good solution as Jakeway suggested. A stripping basket does not work well for deep wading.