For a comparatively concise video that gives you pretty optimum 'value for money' (time wise) the DVDs Travis Haley did are, IMO, excellent (having watched them through a couple of times and tried this kinda stuff out many times with airsoft and a few different firearms).
Adaptive AK is broken down in to very decisive little chunks that cover specific topics so you can just go in and get the info you need. They ended up beign so popular they'e all over the net:
http://www.liveleak.com/view?i=fb7_1350685502
"But he's a yank" well sure but you can ask a Spetsnaz operator and he'll give you basically the same information. Obviously there's a difference in that all these techniques are designed for live fire combat at CQB ranges where the last thing you care about is retaining magazines, plus your mags are far more sturdy than airsoft and you quite likely didn't pay for them. So there are adaptations to be made, but I've found a lot of the more simple plastic midcaps are actually perfectly fine to be flipped/ejected even on to rough concrete (and certainly fine with floor boards, soil, old carpet etc) as long as you're only doing it now and again. I've forcefully dumped my TM EBBr 82/30 mids on to outdoor concrete a couple of times and yeah they got scratched but there was very little deformation of the metal at all.
That said, the tactical or 'lull' reload is probably the most efficient for an airsofter who doesn't want to risk breaking expensive and fragile replica magazines by dropping them. It's not so easy with AKs/G3s and other rock-to-lock magazines but with any gun that follows the AR pattern it's a piece of cake.
http://www.youtube.com/watch?v=Z2bgc-Q0rL8
The worst culprit I can think of is unfortunately the L85 because the mags very often won't drop free (made worse with EMAGs vs the old metal HK ones we used to issue), but there's a method out that'll work quickly and efficiently for most rifles. Certainly more so than the standard "remove empty mag using reaction hand, place away, retrieve fresh mag using the same hand, insert" that is usually the standard.