I agree, it’s confusing. The CFF, Foundation Care, and Pari all have different instructions.
This is what I do--It's a combination of steps from the different sources, taking what's most convenient and what works best for me. (can’t say for sure if it’s “correct”, but I’ve been doing it for years and don’t seem to have any issues.)
Cleaning after each use:
Rinse metal head under warm running tap water. Then place metal head in small plastic container with alcohol and store it there until the next use. Put all other parts of handset in warm water with liquid dish soap (don’t use Dove or antibacterial-they have additives that can cause damage) in plastic container with lid. Swish around to clean and then rinse with tap water and keep parts disassembled so they can thoroughly dry until next use. (CFF recommendations don't say that it has to be rinsed with distilled water, they recommend tap water for cleaning).
Disinfecting once a day:
Using tap water, I boil all of my pari nebulizers (including Altera handset without metal head) for 10 minutes. You can also use a baby bottle sterilizer or Control III. I don’t boil the metal head as soaking in alcohol already disinfects it.
I’ve heard that you have to use distilled water, not tap water, if sterilizing metal head using the boiling method because the minerals in tap water may harm the metal head.
(CFF recommends disinfecting all pieces, including metal head, once a day with baby bottle sterilizer.)
I hope this helps and I didn't confuse you even more!