If your feeling resistance against the drill as you're pulling the trigger, then you're spinning it in the right direction. You also need to rotate the engine by hand occasionally to allow the oil to flow through all the oil holes in the crank to eventually find their way to all areas of the engine. There just isn't a direct path for the oil to travel unless you rotate the crank as well. All the oil holes simply don't align with passages in the block to let you do that. That's why often times, spinning the engine with the starter produces more oil pressure than with just a drill, even though the starter and drill spin at close to the same speed.
