There is another way - it requires some more money and a few more things to keep track of while flying. If you use a second monitor that has a decent focus assist and the focus wheel you can acheive very good focus.
We do this with Secraft trays and mount a SmallHD monitor or anything that you trust for reliable focus assist to it. You feed it from the HDMI port on the back of the remote (works on Inspire 1,
Inspire 2 and M600). Since you can trust your focus assist in this scenario you can use the focus wheel or full size DJI focus hand unit for fine tuning.
We mount the Focus hand wheel with a Secraft EZ Clamp and have it point out the right side of the tray.
Its more to watch as you are flying (especially if you do the FPV screen on your mobile device and the camera feed on the monitor) - definitely adds some cost to your set up - but you can get good manual focus this way.
Here is a link to the components:
Secraft
Thanks!
Michael