The trick I learned in trying to get most fluid out of the vial
was to insert the needle at a 45 degree angle or so, and to tilt the vial
as you withdraw -- gets the fluid into a corner instead of spread out over the entire surface of the vial cap. I usually tried not to re-insert the needle, just tap it to make the air bubbles rise, push them out, and draw in the rest of the fluid. Hope that helps, and good luck!