Exporting references from a central to local bib file

export-references.sh

## using natbib
## when finished adding refs, run
bibexport --nosave -o [LOCAL_BIB_FILE] main.aux
## then switch the \bibliography command from the central file to the local one, ie change
# % \bibliography{[CENTRAL_BIB_FILE]}
# % \bibliography{[LOCAL_BIB_FILE]}

# % with biblatex you would run something like
jabref -n --aux main.aux,[LOCAL_BIB_FILE] [CENTRAL_BIB_FILE]
## and again switch which bib file you're working with
# % \addbibresource{[CENTRAL_BIB_FILE]}
# % \addbibresource{[LOCAL_BIB_FILE]}

Arghh, I've also done this many times, but I have several separate central bib files to pull from. I use an aux2bib perl script

references.bib : $(MAIN)-all.aux
	rm TOGS-all.aux
	cat $(MAIN).aux ch[01]?*.aux > TOGS-all
	mv TOGS-all TOGS-all.aux
	perl $(AUX2BIB) $(MAIN)-all

together with

% Bibliography items originally in separate files
%\bibliography{timeref,graphics,statistics}
% for production, all have been collected in references.bib
\bibliography{references}

I use the Zotero + Better Bibtex to keep the library in automatically sync with a bibtex file

That's different than pulling cited references for a book or paper from one or more master .bib files, whether you use Zotero or not