Body Work Tutorial

Question i have replaced the metal [hand formed pieces] in the cars shell in the areas that required it after i ground/smoothed the welds i filled the area with duraglass just to rough shape. Should i have sealed the entire car prior to applying the filler or am i ok with what i have done? I went to the body supply store today and the guy did not seem to think i had screwed up by doing that he said that old school guys may think its wrong but fillers have improved over the years and not to worry. Should i continue to skim coat and smooth the body prior to sealing or etch primer or what? kinda lost here i don't want to waste time and money doing this, hopefully i have not done something that i have to redo.