hi there brokenglytch:
one thing you might also think about is polyurethane .. or fiberglass resin.
back in the day when i was learning how to stick emulsion on glass it was suggested
by the good folks at rockland colloid to put polyurethane ( minwax i think was the brand recommended ) on the glass
it gives the emulsion something to grab onto ... while you are not using glass, you are using a fabric that is not rigid. i'd
go one step further than eddie
and get your fabric to be the shape you hope it to be, and put polyurethans ( or even fiberglass resin )
both substances will make your fabric more rigid even HARD so you can paint it with emulsion and it will stick to it .
i haven't worked with resin for projects like this, but to fix wooden sinks and it dries clear and rigid, i've used polyurethane and it will
turn kind of yellowish in hue after a while ... and with both you can dunk the fabric in it if you want, and form it and sculpt the fabric until it is hard.
sound like a fun project !
good luck
john