The .32 S&W Long case is really too tiny to make much of an effective snake load, although you could try. Best would be to use very small shot, such as No. 10 or 11 if you could find any. Otherwise use 9s. Use 2 grs. of Bullseye and a .30 cal. gascheck cup-size down, over the powder, fill the case with shot and crimp another gascheck into the case mouth to keep the shot from falling out. Limit distance to about 8 ft., as this will be less effective than the Speer-CCI .38 Special or 9mm shotloads, but probably better than a .22 LR rat shot.
At those close distances, you could just as well use regular ammo, unless you are using them inside fram buildings and don't want to poke holes through floors, walls, plumbing and electrical work.
The S&W Model 31 is one of my favorite walking around guns. I load mine with the Saeco #325 85-gr. SWC loaded with 2.5 grs. of Bullseye for about 850 f.p.s. from a 4" barrel. Very accurate, pleasant and more effective on small game than a ..22 rimfire.