Set the other stainless steel/aluminum cup into the other stove top/hotplate and turn it on to the same setting as the first one.
Wearing the oven mitts (and tongs if possible), carefully pick up the container of liquid bismuth and quickly pour it into the other cup and set the hot cup aside. (try to pour the bismuth without pouring the gray layer on top; it contains impurities which could inhibit the crystals.)
Turn off the stove top/hotplate that the second cup with the freshly poured liquid bismuth is on. The rate of cooling down affects the size and the structure of the bismuth crystals so the slower it cools down the better.