[jyl]

If you can't get snake access and don't have the drain acid, I would try this: fill the sink and close its drain, it won't be totally stopped up but the water column/plug will provide some resistance. Then put some water in the tub and use a plunger on the tub drain. When using a plunger, use rhythmic pushes, you are trying to set up a sort of oscillation that little by little eventually shakes the clog free, rather than trying to blow the clog free with one mighty push.