I used to spend hours trying to fine tune the lenses by taking pictures and comparing them in print or on the screen. Then I learned about DotTune, which improved the focus, but I still was not happy. Finally I bought FoCal, a Pro version needed for TC’s, and it did a marvelous job in minutes for each of my cameras and lenses. Compared to what one has already spent so on expensive lenses and cameras, the cost of the software is really minimal.
Yeah, I've used them all (DotTune, moire screen, Focal, batteries, etc), and for anything I can MFA in my house, Focal has proven to be the most reliable. Longer than 200mm though, and things get interesting due to the amount of working space needed, getting a good focus chart aligned, and finding good enough light to shoot in. This past spring I set up a basketball in long grass to MFA my 100-400, 400 DOII and extenders. Now I have a 500 that I've never done accurate MFA with, but I've taken enough shots to where I could see a pattern of focus being slightly off, and I've gotten it spot-on now. haha Even after all of that, it's trial and error, tons of photos having been taken and examined. After a while, small adjustments made to get zone of focus perfect.
Ruby-crowned Kinglet, first one I've ever seen!