From what little I've done with molding (except for latex and silicone facial appliances...done a bunch of those in my time), plaster should work fine for latex and any other pliable material. The thing about using it for resin and other rigid materials is that it is a pain (at least for me) to de-mold the final product. Even with a good mold-release agent, I just can't seem to get rigid pieces out of a rigid mold without a lot of cussing and a good deal of damage to my cast or product.
I have used some rather cheap and "down and dirty" materials to make molds for rigid pieces, though. Cheap silicone caulking from the hardware store can be used for quite a few things. I doubt it would last through very many pulls, but it has worked pretty good for me for one or two pulls of small pieces. I've also made molds out of wax, clay, and even hot glue sticks by melting the stuff and pouring it over my sculpt. Again...not very durable, but I have always gotten multiple pulls from the molds.
From my limited experience, it seems the key to a good mold for rigid items is flexability of the mold. When I have the cash, I try to use silicone to get the details and a plaster bandage "shell" to help it keep it's shape. The bandages can be removed so you can get the item out of the mold by peeling it off. Then put the shell back on and store it or do another mold. Probably not exactly the best way, but it's all I know and haven't had problems yet, so I'll stick with what works for me for now
. By the way...this also works well for alginate face and head molds to get yourself a good likeness to sculpt appliances on (and I have done that a lot
).
Hope this helps a little and others who know waaaayyyyyyy more than I do will chime in with better tips. Mine are just my cheapo, whiskey-tango ways of getting things done on a tiny budget .