Thank you Waterwingz. I modified the "Remote button" script (similar to
http://chdk.setepontos.com/index.php?topic=8039.0), which works almost (see below) perfectly, since I don't need sync'ing on release, but rather shooting on button press. I load the script below (saved to CHDK/Scripts/remote.bas), then press <ALT>, then the trigger and voilĂ !
@title Remote button
while 1
wait_click 1
if is_key "remote" then click "shoot_full"
wend
end
However, I also need to adjust the following settings (which won't change throughout the photo session)
1. "macro" distance (manual focus?)
2. brightness (ISO and f-stop?)
Do I set Disable Overrides to "Disabled" and make the settings there, here in the code, or elsewhere?