I don't soft reset much, but Ho-Oh in Pokemon Sun and Moon I did because it was the Rainbow Pokemon and we were in the Rainbow Region. I also really love shiny Ho-Oh because it is the true Gold and Silver pokemon. And just to answer, yes, yes I did get Shiny Ho-Oh :D As for how many, no idea, I found it best not to keep track as it just makes it worse. I will say that I am almost certain it was less than 200 Resets.
I am also currently Soft Resetting for Latias using the Eon Ticket in Omega Ruby. Which I haven't gotten yet, but I've maybe only reset 50 times.
I have tried to Soft Reset for Ultra Beasts as well, but I grew board of that, but will eventually do it again. As well as Soft Reset for Latios in Ultra Sun.
I don't recall soft resetting anymore than the times mentioned above. Other than when I used to lose to Elite 4 or accidentally knock out a Legend or run out of balls to throw.