Create a focus magnifier that is extreme. From Friedman.
Focus Magnifier – for even greater focusing accuracy, the camera will show you a magnified view of any portion of your frame, allowing you to focus critically. (Peaking Setting can still work here too, but sometimes the contrast isn’t high enough to show the color.)
This is a function that you have to assign to a button – I use the C4 button. (MENU → → Operation Customize → (Images) Custom Key/Dial Setting → [Choose a button – I recommend “Custom Button 4”] → 26 → Focus Assist → Focus Magnifier.
Once assigned, hit the Focus Magnifier button, then use the arrow keys (either on the Multi-selector or the rear control wheel) to tell the camera which part of the viewfinder you want to magnify, then hit the center button.
Focus critically. Want more magnification? Hit the center button
again. Then hit the shutter release button halfway to go back to Live View and shoot at your leisure.