The best explanation of how a SHS works is to look up Fred Veio's book. I am going to over simplify here a little. The idea is you sweep a slit past an image of the sun and bounce it from a diffraction grating. You then sweep another slit across the spectrum at the same rate. There are quite a few ways to do this in practice. One is to take the rotating prisms from an old movie projector. I have seen some large 8 sided prisms that would spin inside a projector. With two of them you can use them to sweep an image by a stationary slit.

This mechanical task is the key to making a successful SHS. I have seen at least three different ways of doing it but I am sure there are many more. It takes a fair amount of planning to make it all work.

You can measure your diffraction gratings by bouncing light of them and measuring the spectrum. If you bounce white light off it and project to a white card a know distance away you can you the dispersion equation to calculate a rough estimate for the grating frequency. If you want to know exactly you can use a sodium light or something else that you can know the exact frequency of the lines. Then if you know the distance between two lines and the distance from the grating to the projection screen you can calculate the spacing. This will not tell you the efficiency however.