How do you do it?  I shot a Police Pistol Course match tonight, and loading the second 6 rounds out of the 12-shots-in-20-seconds stage into my SW19 was next to impossible for me to do in the time given, as a lefty.
Where do you position the speed loaders on your belt?
What do you do? --which hand goes where?  Do you hold the pistol with your opposite hand and work the speed loader with your left hand?  Which hand ejects the shells?
FWIW, I'm using HKS speed loaders, nothing spring-activated.

lokt;

Much more easily demonstrated than described, but here goes...

...after the last shot is fired, activate the cylinder latch with the thumb of the strong hand (left) by bringing it over/around the back strap (yes, you could...maybe...do it with the index finger, but the thumb seems to work better for most) and pushing forward. Push the cylinder out with the right thumb while making sort of a "V" with the thumb and fingers of the right hand...the thumb will go through the frame and the fingers will "cradle" the gun under the barrel / triggerguard area.

Turn the barrel straight up and use the index finger of the right hand to push the extractor rod and eject the empties, then turn the barrel down...muzzle toward the deck...and keep outward pressure on the cylinder with the thumb while using a finger or two to prevent it from just spinning freely...or closing part way, etc. Insert speedloader...which should be carried in a position where you can reach it easily with the strong hand, and grabbed from the belt by the "barrel" of the loader, NOT the knob...then use the fingers to twist the knob of the loader once inserted. Let the loader drop (you waste time if you throw it...gravity will work for you here) and close cylinder while you raise the revolver back to the target and resume firing. "Smooth is fast"!

You may see other lefties who have worked out a different system, and that's fine, but the method I have described has worked very well for decades and is both fast AND secure in the field. Be careful not to twist the knob of the loader as you draw it frim the carrier, as this will activate it and your ammo will be on the ground...if that happens, drop the loader and grab another...you DO have another, don't you? Ha!

Be certain to keep chambers clean so cases don't stick, or live rounds fail to chamber completely.

12 rounds in 20 seconds is plenty of time if you are smooth. 1 1/2 sec, to draw and fire the first shot, 1 shot per second for the next five, unload, reload, then one shot per second should allow you easily 7 seconds for the reload...duck soup!

Good Luck

Thanks, Ikor.
I've had the chance to practice that method a few times, and it is getting faster.
Thanks for your help.

And you're welcome.

The only other thing I might add is to try using the palm of the strong hand to smack the extractor rod rather than the index finger of the weak hand. While this does take just a fraction of a second longer because you cannot be grabbing your speedloader at the same time you are ejecting empties, it does have the benefit of being more "positive" in the event you have a stuck case...not all that uncommon with k-frames using magnums once they hear up a little.

It is also more likely that you won't miss the rod if forced to move while reloading...not something you would want to do, but maybe necessary if someone is taking your cover away piece by piece with a long gun of some sort...or reloading in the dark, etc. where you cannot see the gun. Either way, practice until you can do the entire reload smoothly in the dark, or behind your back, etc. by feel alone. Then you will know you are getting there. (Then we can work on the strong-hand only and weak-hand only reloads...Ha!)

Good Shooting

Alright, I'm curious the strong hand and weak hand only reloads...  
Can you elaborate on preferred technique for this?