Double action guns
There is no big deal about SA, DA/SA or DA only guns. They are fired the same way. This is one of those subjects that keep the gun mags going and is mostly a lot of crap. I find that SA guns like the 1911 are the easiest guns to learn to shoot well.
With that said, there is no big deal dealing with the transition from the first shot being DA and the rest being SA. The only problem is that most folks at the range cock the DA/SA gun so that all of the shots are SA. By doing this, they are cheating themselves by never learning how to use the DA trigger,
I have shot DA only guns, owned DA only guns, and taught the use of DA only guns. I am not covering Glocks as DA only guns, because they are not. The DA only gun was developed for the police as a measure of safety to overcome insufficient training. In my view the DA only gun is a clever solution to a problem what does not exist.
The well known solution to shooting any of these guns is to press the trigger smoothly to the rear until you get a surprise break. What ever you do, do not stage the trigger. I do suggest that for all but the DA only guns that everyone learn about trigger reset and use it all of the time, until it is a firmly embedded habit. Using trigger reset allows the shooter to shoot faster and more accurately.
BTW, last year we had a police officer shooting a SIG (DA/SA) in a class. In less than 2 hours he was shooting the SIG very well and reported that he aced his quals a few months later.