If the items in question are small, them a multiple mold works just fine. We do sake cups this way, and tiny vases. For anything bigger than a teacup, double molds may work, but more single molds work better than gang molds. When there is enough plaster to pull the right amount of moisture, they get heavy quickly. Add the weight of the slip, and dumping them is a two person job. Also, the slip you dump tends to go everywhere, sometimes into other molds in the gang....
You might consider using a different height work surface. Either use chocks to raise the table you have now or change your chair height. Perhaps sitting on a balance ball, even. If you have a variety of heights available, you can move around as you work. If you work standing already, get some good floor mats.
How large are the birds? What size rod or wire you use for the legs will depend on how much they have to support.
I suspect that you will have to have some of the rod handy when you sculpt the birds, because you want them to balance standing up.
If they are small, stiff wire, like hangar wire will work, you cut it with a pair of tin snips, available at any hardware store. For larger pieces go to the hardware store and browse in the solid rod selection. There will brass, copper, stainless, aluminum and steel to choose from. Most aren't very expensive, so you can experiment. Heavier rod gets cut with a hacksaw. You might be able to use tubing, which is sometimes cheaper.
You probably won't be able to fire the legs with the bird itself, but will need to make the holes for the legs as you sculpt and be prepared to drill them out after firing.
Just an idea from years of playing with paper making- take a sheet of unsized abaca and wet it with a sprayer. Press it onto a sheet of glass, either a window with good sun or a sheet that can be moved into the sun, and smooth it with a roller. Let it dry in the sun. When you peel the dry sheet off it should have one very smooth, calendared surface. It should look almost glazed. That might tighten up the surface enough to need just a light rub with bar soap to act as a release agent.
(I drove my studio mates crazy by covering the huge windows with fresh sheets once in a while. The linty look between peeling off and a through washing just wasn't attractive to them, I guess.)