I'm curious about this.
If you are diving wet, and are in cold water, what is the proper way to fill the bag? You don't have a DS hose to pull off, and then you have to use your octo if the bag is open anyway. Plus those hoses can be a bear to get off under water and with thick gloves on anyway.
In my AOW class, we used our octo as well, with an open bag. The instructor said to just use a little gas, and let it go. This was for surface marker purposes, not lifting. He showed us a closed bag, and said you'd fill that by disconnecting your lp inflator from the bcd, but we didn't actually practice that. We did practice using an open bag on a 40 pound weight belt. That was done with octo inflation as well.
If you have a better way, I'm certainly open to suggestions.
I don't have any bags/smb yet, but intend to get one of the larger smbs before I go back to the ocean. I currently just dive lakes and springs.