So, I have one, too. Unfortunately, I don't think I know how to use it. I'm going to practice, though. Have you ever used it as a safety-stop anchor? I really need to learn how to use mine! I've carried it for ages, and never even tried deploying it.
I practiced it once during safety stop. It has 20' long string. I got tangled with the loose line as I ascend then, so I added a home-made reel out of 1/2" x 6" PVC tubing (as shown on the picture I posted here earlier) to wrap around the loose line as I ascend. It worked well on the 2nd use in Jupiter, FL.
The whole DSMB with the tube reel fit in their original pouch & in my BCD left pocket. The only 2 safety gears that are mounted outside my BCD are the whistle (hanging on my left chest D-ring) & Dive-Alert, which is snapped on between the BCD power inflator and LP hose.
I haven't use the DSMB as safety stop anchor. I rather not use it as safety stop anchor if there is not much current. Whenever I need to stay in the blue water with no current for safety stop, I rather focus on controlling my 15'-18' depth by buoyancy (deflating / inflating the BCD), while watching my dive computer, and not get task loaded by reeling and unreeling the DSMB string in addition to maintaining my depth.
It would be different if I get blown away by swift current. Then I would definitely use it as my safety stop anchor line and marker to the boat above to find and follow it. The swift current would drag me with it, so the line will always be under tension and a lot easier to control my depth with the 20' line. Then I would fill the SMB with air, let it rise to the surface by unreeling the line to the end of the line and hang on to the 1/2" x 6" PVC tubing empty reel. When the 3-min safety stop is up, then I can slowly reel in the line which will pull me back to the surface.
Hopefully the boat will be closed by, when I'm on the surface. If not, I'll blast away the Dive-Alert air horn or flash the boat with the mirror or flashlight, whichever works for them to see me.
If I'm floating for an hour without any boat seen in horizon, then I launch the PLB1 that will beam 5 watt 406 MHz signal directly the sky to NOAA Search and Rescue satellites to let them know that I'm lost at sea.
I haven't considered to get the Nautilus Lifeline (NLL) simply because it uses 1 watt VHF radio frequency signal from it to nearby boat if the boat does listen to the channel 16 (156.8 MHz for marine international calling & distress channel) or whatever channel that your boat and your NLL agree to use for radio communication if you are lost at sea for the older version of NLL. Such surface to surface radio signal from your NLL antenna to the boat radio antenna is probably good to a mile away. Some boats other than your boat may not be even listening to channel 16 and cruising by you without seeing you while you are snoozing & bobbing on the water.