I don't really know what works for other people, I usually wear them down a little, playtime or whatever and then work.
Work him on a leash, teach him to heal (to your non gun side). Some people prefer them to heal facing backwards, but you don't see that much anymore. If you keep his head up a little, he is unlikely to lay down. I use a combination of the leash to keep his head up a little and/or hand signals (If there eyes are looking up they are unlikely to lay down). Mine seem to pick up the necessities with a combination of hand signals and voice commands. Later you can use either one. Knowing when to stop training is the hard one and varies from dog to dog, it's hard to get just right. I usually try to stop on a high note.
I also train mine to a two tone whistle, one is a steady whistle, the other a trill, like a Policemans whistle. The steady tone means recover and heal. The trill whistle means drop in place and freeze. We have a couple of group hunts a year, and there may be thirty dogs along. Most all of them are trained to drop and freeze when somebody blows the policemans whistle. I don't know if you will need this or not, but it may be helpful sometime somewhere and gets them used to following commands.
A million books and videos out there, I've had both my daughters give me dog training books. Probably because I just let my dogs be dogs a bit too much. But heck it is supposed to be fun.
I'm sure some dog expert will be along soon to tell me I'm doing it all wrong.