Even a standard funnel designed for motor oil(suggest using a brand new one)will work as it will have a narrower opening. Try to find one where the opening is not too narrow or you will be all day trying to get the sand to move through it into your stands. I have found that an even better solution than straight sand is a mixture of lead shot and sand. Number nine lead shot works well and can be found at any store that carries shotguns and the like. The reason you combine it with sand is that even small lead shot will leave a small amount of air between the pellets. Using sand fills in the small spaces left between the lead shot pellets. A 60/40(pellets to sand) mixture of this type will offer more mass in a smaller area as compared to sand alone, which will allow you to leave part of the column unfilled if you find that, that sounds better.