Trouble is, the closer you get, the harder brenz method becomes due to more exaggerated camera angle changes.
Before I had 2 bodies I used a thinktank belt with pouches. Don't need to use lens caps, and lens changes only took a few seconds. There is a good/fast technique using your index finger, maybe you know about it?
Lastly what are these 'tests' for, and where are you getting these models.. MM or something?
Edit:
Also I can't tell if it's artefacts from my retina screen, but are you adding grain these days?