Having some surface to set the bottle on while filling is a VERY good idea. Idealy, you should be using one hand to hold the wand/stopper firmly (not pushing with all your weight, but like you would grip a power tool, with firm control), and using either your index finger on that hand, or your thumb on the other hand to "burp the stopper." Once liquid beer reaches the bottom of the stopper, stop "burping the stopper" and close the tap. At that point, count to 10 then simply remove the stopper and wand from the bottle and move it to the next.
Fat Toad Brewery