Yes, TAPPING with the hammer is correct. Grip the hammer LIGHTLY with the forefinger extended and pointing up the handle, we aren't pounding nails, but MASSAGING the metal back into place. Take out your agressions by PUSHING the dolly hard against the back of the dent, don't just hold it there, and use a sliding tap with the hammer face. Proper preparation of the hammers goes a long ways towards making bodywork easier, as with most tools they require "tuning", they don't come from the factory ready to use.

Hand filing and sanding is still the prefered method for finding the high/low spots and smoothing, but there is some technique involved to making it easier and more effective. A power panel and DA sander makes finishing bondo go a lot quicker but I still hand sand my final coat(s) of surfacer putty.
Once you learn the "secret" techniques bodywork goes pretty quickly.