preparing for shabbos

One of the examples of mitzvah bo yoseir m'b'shlucho is preparing for Shabbos; the gemara records how various Amoraim would personally try to help with the Shabbos preparations. Interestingly, the Aruch haShulchan (250:3) calls this a hidur mitzvah and writes that one is yotzei through ishto k'gufo! The Shmiras Shabbos (42: footnote 195) quotes R' Shlomo Zalman as holding that unless one has some pressing need to do other work or is engaged in learning torah one should not only help by doing one act to prepare for Shabbos (which at least minimally fulfills the mitzvah of kavod shabbos through preparation), but one should personally attend to every act that needs to be done, because on each and every act of preparation the sevara of mitzvah bo applies.