Reloading under pressure is certainly an art in its self. The best thing i can say about it is practice...
Personally i run 7 30 round mid caps and a small pistol style speed loader. it gets me through most engagements. If i know i'm going to be running a longer mission during a bigger operation i will my magazines, speed loader and a small bag of ammo
with a rubber band around it to keep noise down. I also put some kind of marking on my magazine because when i do a speed reload i often leave them on the ground. Ill pick them up after i get tagged or the fire fight is over and friendlys are offering me cover.
Before worrying about reloading procedure you must first make sure your equipment works for you. Make sure your magazines are faced so the mag curves to
your right when in your pouches.
I utilize the beer can grip when i reload. This means when i go to pull my magazine from my pouch i turn my hand so my palm is facing away from me and my thumb is towards the ground. I grab my magazine with a firm grip then pull the mag out of its pouch, rotate it up then into my mag well.
As far as reloading magazines goes there is two kinds of reloads to consider while airsofting. A tactical reload and a speed reload.
During a speed reload your under fire and have to change magazines as fast as possible. This is, for that reason, the hardest to master. I often times will eject my spent magazine by pushing mag release with my fire control hand (right hand) and rotating my gun clockwise to fling the mag from my gun. At the same time i use the beer can method to reload with my action hand (left hand). Takes me maybe 2 seconds.
During a tactical reload i use my dump pouch (holds 4 mags, 5 if i cram it in tight). Spent mags are put in dump pouch while i reconsolidates magazines that are furthest from my center to the front making them easier to find during a speed reload. I also utilize the beer can method here as well. If you have time
and cover feel free to reload your spent magazines with your speed loader and place them just behind your other magazines.
The most important thing to remember is constancy and repetition. Build up the muscle memory. Do this till you can do it blind folded and under pressure. If you can reload while blind folded then you don't have to look at your gun. That means you don't have to lose situational awareness!
You should also get a hold of Magpul's Art of the Tactical Carbine. They go over all kinds of things from beginner tactical stuff to advanced stuff. Its a great movie and you can learn a lot that transfers to airsoft.
http://www.amazon.com/Art-Tactical-Carbine-Chris-Costa/dp/B001JEQPKK/ref=sr_1_1?ie=UTF8&s=dvd&qid=1295166271&sr=1-1The following link is the dump pouch i use if your curious what i mean by small dump pouch. I highly recommend Cordura made products.
http://www.ebairsoft.com/foldable-dump-pouch-p-2363.htmlThis is the plate carrier i use. It also has the dump pouch attached to it.
http://www.ebairsoft.com/cordura-land-cirss-vest-delux-version-p-2467.htmlIf you have any questions shoot me a PM
-Chip
EDIT:
If you haven't already purchased them DO NOT go cheap on these! Your best investment next to replacing the shorts you used your first time on the field is your magazines. I cant stress this enough.