changing lenses

Does anyone have a specific "technique"?
I find i need a surface to set the other lens on with the back cap of my current lens
and while photographing a gig (Small gigs I shoot with my 50/1.4 and my 10-17) its incredibly hard!

I keep all my lenses in the bag rear cap upwards.
1: With the camera face down, I remove the attached lens and put it in the bag where the camera normally sits.
2: I then remove the rear cap from the lens I'm about to use, without taking it from the bag, and put it on the lens I've just removed. This part is the most difficult with Sigma caps as they need to more or less register precisely on the mount.
3: I fix the required lens to the body.

I hold the new lens in the right hand, rear cap slightly loosened. With my right thumb I press the lens release button and with my left hand loosen the lens on the camera. I then remove this with my left hand, remove the rear cap also with my left hand and then seat the new lens with my right hand. Then both hands are free to attach the rear lens cap and store away the previous lens.

The time any lens is off the camera is therefore very short.

Sounds complicated to describe, but it's actually quite easy.

I usually find a flat surface for the lens I'm about to fit, etc, etc.

I replace Sigma and Tamron rear caps with Pentax or other caps that are easier to fit.

I just learned to juggle...
seriously...I wear a hip pac bag and do my lens swap over the bag in case something drops... I pay attention to the red dots, and do a swap with the camera facing down, one lens in my right hand( thumb and pinky hold), camera in the right hand also, one finger (same one I use to wave to other manitoba drivers) on the release.
A turn of the left hand pops the old lens off the body, moves the (already loosened) cap off the new lens (left thumb and index finger) to the old lens, place the lens in the bag and then snap the new lens on.
takes three seconds (or so) start to finnish.