The DSMB (D for delayed : you send it at the end of your dive) tells the boats around (including yours) where you are. It can be a life-saver. Notably when the place is crowded with boats (common in Egypt). In my opinion, it's a mandatory piece of kit, at least for drift or "serious" diving (take also a small LED torch with several hours of burntime, like this the boats looking for you after your wild unplanned drift are almost sure to find you eventually ... at night !)
For me, though it's doable, it's not such a good idea to inflate it after you surface, unless you are so close to a reef that even the zodiacs cannot come close and harm you. The DSMB is here also to tell all boats: stay away with your nasty propellers, there are divers below. So send it from your safety stop, or even before. Typically, a good captain on a Red Sea boat expects to see your DSMB 5 to 10 minutes before you surface. Like this, he knows where to pick you up in time.
You can use a DSMB with a reel (or a spool) ; or without, with only some line wrapped around the DSMB and hold by bungees (I use a SS carabiner at the end of the line to weight it, with two bungees on this carabiner ; I wrap the line around the SMB, use the bungees to tighten it all, and clip the carabiner on my D-Ring ; I deploy the entire line for use and the carabiner acts as a weight. I use also a finger spool for deco dives).
In that last case, because of potential surface current, the length of line must be greater than your deployment depth. Eg if you send the DSMB at 5 meters depth (= safety stop) it's good to have 7.50 meters of line, in case. The cheap line usually sold with DSMBs is not any good, replace it by some decent 2 or 3 mm line like those from climbing accessories. A drawback of this no-reel way is, you need a bottom not too shallow (12 to 15 meters minimum) so the line, that you're fully deploying before sending the DSMB, doesn't get entangled on the bottom ; usually not a big problem, at least where I dive.
Using a reel (or a finger-spool, less bulky and simpler) gives more possibilities but it's another item to carry. Also take care with spools, the carabiners (with two slipping gates) usually sold with them are prone to get unclipped while jumping from a zodiac, etc ... so I suggest you double them (= use two carabiners parallel to hold your spool) or find your own way to do it safely.
Tech divers often send a DSMB from the bottom (= beginning of their ascent) to tell where they are and to have easier control of their ascent speed. But that's another story, rec dives are usually multi-level and for these dives one often doesn't need such a long line (apart from some special circumstances that Blackwood details below and that make a reel or spool with enough line really handy).
After your DSMB is on the surface, you swim underwater where you want, while pulling on it - like a dog on a leash. It's normal that sometimes, with surface current, the dog is a bit hard to master. You give leash or you take leash depending on the current, but usually it's not so strong that you cannot stay connected to your DSMB while doing your stop.
DSMB deployment needs some practice to be done properly and safely. Check around you to have some demonstrations - and then practice - if you feel not completely at ease with it.