Smoothbores
The first smoothbore I owned was an old New Englander.
We ground off the percussion made a touch-hole and added a flintlock.
I've owned about 20 since then.
Singles-Doubles and Swivelbreeches.
Mine don't have chokes, so I can shoot patched round ball and shot. I've killed deer with a Tulle 20ga at 110 yards. (The best shot I've ever made with a smoothy.)
I hunt small game and have shot sporting clays with them. (flinters) I can only shoot about 10 to 15 targets out of a round.
Some of the shots a multiples and most of my guns are single shot.
I almost always use flintlocks but have a good selection of percussion guns. I shoot a lot of competition and most of these go by date, 1760-1840, 1830-1880, etc. You can use any gun manufactured in those time periods.
My father says that what ever you can do with a cartrige gun I can do with a flintlock. It's his fault... He bought me the first one in kit form to keep me quiet.
I can't tell you anything about books. Most books on smoothies are terrible. Not enough info.
I would check on Muzzeloader Mags web site and ask some questions there. I'll give you a brief rundown on what my loads are like.
For my Christian Springs 12ga.
1. 70-80gr. of fffg
2. pre-lube felt wad
3. In the same powder measure I load about 1 1/2 measures #6 shot.
4. pre-lub felt wad
With this combo I have won a dozen smooth bore matches and killed a lot of game.
I must warn you about the kick. What you have done is sort of plugged the barrel. As you load you will notice how much air pressure pushes back on your wads. Just take you time to load and everything will work out fine.
Prime with ffffg
For turkey you might want to add some larger shot. Make it like a duplex load.
With the new New Englander you can shoot all types of shot so play around and have fun.