add note about running without filter first

README.md

@@ -42,3 +42,7 @@ Adding -f will filter the groups under consideration to only those listed in
 config/chat_list.txt
 
     $ ./run.sh -c ~/.config/Signal -f
+
+You might want to run the command once without filtering, then paste the chat
+name column from the spreadsheet into config/chat_list.txt and narrow down to
+only the ones you care about and run it again with -f.