A friend of mine does sand casts of brass parts for muzzleloaders and sailboats, I saw how he made his parts and stole one method that for making ingots. I use a pan filled with cat litter, make the ingots the size I want shaped out of aluminum foil and push them into the cat litter and then pour the ingots, when all the foil ingots are hardened, pull them out and reline the litter with more foil. This is a very good way to pour lots of ingots very quickly. You can probably substitute sand for the ingots as that is what my friend uses with his brass. I have quite a bit of cat litter around so it works for me.
regards,
Graycg