Not sure what you mean by switch to reserve... There is no need to switch the lever unless you swap in a new propane cylinder. It sounds like you are waiting until both are empty to do the swap. This waiting will cause you to run out of propane.
When the indicator is red, the lever is pointing at the empty cylinder. Change it. Then switch the lever. Repeat. Keep a calendar to mark the days you swap in propane to get a pattern.
Once you have two empties sitting on the ground by all means get some assistance and have the pair filled. If help comes next day and the indicator is red again take three cylinders down for refill.
If you need assistance swapping cylinders... consider an extend a stay connection with a 100# rented cylinder and have the propane truck come to you.