I had an epidural for labour, which was then subsequently topped up for labour. I also work in obstetric theatres, so see spinals inserted all the time. Heard the spiel, and recited it myself a few times. What I experienced while having my epidural inserted was very similar. As a PP stated they're very similar, except the epidural leaves a tube in situ. It's also inserted into a slightly different space, so it acts much quicker than an epidural.
Basically you'll have a cannula inserted first. Ask for emla cream ahead of time if you want, but it's not too bad.
As for the spinal itself it starts off with the anaesthetist greeting you then going off to get themselves sterile and their drugs and equipment ready. Then the anesthetic assistant (usually a nurse/ODP) will have you sat in the edge of the bed (if you aren't already) who will check your identity (hope you know your own name and date of birth!) and ask you a variety of questions (allergies? loose teeth? metal in your body?) while hooking you up to the BP machine, and exposing your back.
Next it's time to clean your back. My trust uses a cleaning solution spray to sterilise your back. It's very cold! Other trusts have the anaesthetist paint your back with a similar solution.
Next a sterile drape is stuck to your back. Don't touch! And you'll be asked to assume "the position". Basically you relax and drop your shoulders, and curl over your bump, pushing your lower back out. This position opens up the spaces between your vertebrae. The anaesthetist will feel the bones of your back to identify the area they're going to inject.
Next is the local anaesthetic. It's a sharp prick, then a stinging sensation for a few seconds then the area goes numb. This is, imo, the most painful part of the entire procedure. Once that's done, it's time for the spinal needle itself. Try to hold still as you can. It shouldn't hurt, but you might feel some pressure. If it is too uncomfortable, tell the anaesthetist and they can give some more local to help numb the area further. You might be asked if you feel the needle more on one side or in the middle. Sometimes you can get an electric shock sensation. Once the needle is in the right place, the medicine is injected. You might feel a warm sensation trickling down your back and legs. The needle is removed, and that's it!
You'll be encouraged to lie down straight away as it's pretty fast acting. You might feel pins and needles as your legs gradually go numb. You'll lose the ability to move them too. Your BP will be measured every minute from now until baby is out. You'll also get your heart rate and oxygen saturation monitoring attached at this point too. The bed will also be tilted to the left as well, since you shouldn't be laid directly on your back. After a few minutes, the anaesthetist will measure the progress of the block. Usually this is done with a cold spray. The nerves that carry pain carry cold. If you can't feel cold, you won't feel pain. They'll spray it on your arm to demonstrate how cold it is, then spray it up your body from your pelvis towards your boobs. They'll want to know 1) if you feel anything, 2) if it feels cold, and 3) when it starts feeling cold.
After this first check, you're usually numb enough to have your catheter inserted. Once that's done, another cold spray check is done, and usually you're numb enough to proceed. Sometimes you need a little longer, or it's not quite high enough on one side. A bit more time, or tilting the table often remedies the situation. Your anaesthetist will be in constant communication with you the whole time, and will discuss options with you should the spinal not have worked, or isn't working completely.
Once the anaesthetist is satisfied, and all the hullabaloo of the WHO and draping is over, one final check is done by the surgeons prior to incision. You should be so numb you'll have no idea it's happening. Assuming all is well, it's the actual C-section itself, and this post has gone on long enough. You'll feel movement and pressure, but no pain. Your legs will be completely numb for a few hours, but sensation will gradually return.
Hope this essay helps!