There are many brands of spray in lines on the market , and most are very similar. Application is mainly what sets them apart these days.
Think about it like shotgun shot. A sprayer set up to shoot oo buckshot size droplets will produce a heavier, thicker, gripier texture, but use more product. A sprayer set to shoot birdshot size droplets will give you a smoother, thinner , less protective texture and use less product.
Most kits come with epoxy and hardener, when mixed give you about 1/2 gallon and run $80-$100 a kit for decent stuff. They say it's enough for a full size truck. It's not, unless you really spray it thin. That's is why most dealer or factory liners feel smoother and thinner with a texture of sandpaper. To me, not worth it.
I'd go somewhere where you can deal directly with the guy going to spray it. Look at his work and let him know what kind of texture you expect to see. I'd also clean the entire truck with dawn before taking it in and ask for a photo of the prep work be text to you before he sprays it.
Or. Just do it yourself.