1. Is there a preference for which air source (primary, octo, mouth) to use for inflating the SMB?
I use my long hose. Exhaust gas works but sometimes can need 3-4 breathes which will screw buoyancy before its full enough. Just be careful if you use a reg in cold water not to freeflow it due to ice.
2. What is the typical depth from where divers shoot SMB's? Safety stop? From what depth should I practice doing it?
I send mine up from as deep as possible (so wherever the bottom is or 20-30m or whatever) - that gives the boat the longest possible time to locate me and i wouldnt have drifted as far from the wreck as i would have had i waited until shallower. It also has the effect of being easier to fill at depth in terms of being full at surface.
3. The video is great for pointing out the steps but how long should it really take a diver to shoot an SMB? If you find yourself in a semi emergency for instance. Let's say you have an OOA diver sharing your air and now you want to shoot a SMB before you surface. Surely you'd want to do it as quick as possible. How quick is that?
Dont rush it. A minute is fine.
4. If you're not wearing gloves I can imagine that running the reel between your fingers as in the video clip can hurt if it runs particularly fast. Any ideas?
A few idead. With SOME spools you can let it pull up a metre or so above you and it'll drop into your hands. Only work with no wind, no current and good visibility though. Other option is to clip the bolt snap to the line and let it run through that while you hold the bolt snap.
Or just use a reel instead of a spool - these are FAR easier!
5. Any tips on maintaining good buoyancy while inflating the SMB and before sending it to the surface?
Slightly negative and finning to start then gradually finning down prior to release. Get buddy if you have one to maintain depth so you have a reference and WORK SLOWLY. Also take care not to breath hold while concentrating on the task as this'll mess up the buoyancy. Try not to use your computer as you're chasing the numbers which isnt as smooth as a non moving visual reference.
6. Is there a good/efficient way to wind the line back on to the spool as you make your ascent? I bought a Mares compact reel (image below), thinking it would make it easier but it doesn't. It's not such a great design and now I'm thinking of removing the handle and everything so I'm left with only the reel. My question then is, how do you conveniently reel in the line again?
First thing, snap all the red weird plastic ****e off the spool - it serves no purpose. Then you use the bolt snap to wind the line onto the spool (clip line through bolt snap and use it to guide the line on).
Or use a proper reel not a spool - as above a good ratchet reel makes deployment and winding far far easier.
I really dislike the "random large chunk of line with no reel or spool" method you see at some tropical locations. Entanglement hazard waiting to happen, a boat prop snag waiting to happen and a great way to damage the reef too if its got a weight on the end. Spools and reels arent difficult.