I just turn the main system off via the remote control and use the slave receiver normal. The slave moves the dish and selects any channel on any transponder. I never have them both on at the same time. When I turn the slave off via the remote, I can use the main STB to move the dish and watch any channel I want.
Is this possible only on certain STBs?
I tried this on my Merc-II (primary) and Skywalker(slave) and it didn't work. When i turn the Merc off through the remote, the Skywalker can't get any signal on any polarity.