Sorry, I've been to the pool school, read countless posts and watched many videos. None seem to have my pool configuration. What seems clear is that you must get the sequence of activities right in order to avoid disaster. So I'd appreciate if someone who has experience with my kind of setup could validate or correct my process and/or assumptions about the setup.
Note - see attached photos. Skimmer 1 requires two plugs (lower is for main drain, upper is for skimmer), and skimmer 2 only requires one plug.
1. Backwash/Rinse filter and drain.
2. Lower water level to 1" above the light fixture (approx. 1 foot below tile/skimmers, but still slightly above the returns).
3. Bilge-pump skimmers and then plug them (all three plugs).
4. Set MPV to Filter.
5. Remove pressure gauge from top of filter housing and insert air compressor line (~25psi).
6. When all water is purged from returns, plug them and simultaneously unplug skimmer 1 (both lower main drain and upper skimmer plugs).
7. Replace upper plug in skimmer 1; when main drain blows bubbles, remove upper plug and quickly insert lower main drain plug.
8. bilge-pump skimmer 1 again and insert upper plug; simultaneously remove skimmer 2 plug.
9. bilge-pump skimmer 2 again and insert plug; simultaneously turn off air.
10. Disassemble filter, clean filter element and reassemble loosely.
11. Open and clean strainer, remove strainer plugs and close strainer.
12. Install cover.