I did try that on Antares then slewed to Jupiter and found I was a little out. So either my baht mask wasn't precise enough for that FL or I didn't focus accurately enough. I realise you can focus by small increments which might be fine for deepsky with a mask because you can see the changes in the pattern but I find it useless on Planetary. I need to go in and out of focus and travel quickly through the sweet spot to judge where it is. When everything is wobbling and bouncing around I'd be buggered to notice if my current focus is better or worse than the previous step I was at. There's nothing obvious to me visually to compare. I don't know how people can judge this.
Maybe experience. But catching that fleeting moment in the soup and say "yeah, I'm in focus now" well, that's not my forte.