Just some thoughts: When I do this I put in an empty magazine and lock the slide to the rear. Then when I insert a new magazine I have to release the slide in some manner as part of the reloading process. After that I lock the slide to the rear again and leave the magazine in the gun that I just put in, and then reload with the next one on my belt, which is in a different place a little farther to the rear. That way I get practice reaching for a different magazine in a different position so that my muscle memory doesn't make me reach where the empty magazine holder is.
Thats just what I do, others, I'm sure, do other things.